#cssselectors

Boost Your CSS Skills with Compound Selectors!

🚨 NEW VIDEO ALERT! 🚨 

 Ready to take your CSS skills to the next level? In today’s video, we dive into CSS compound selectors and show you how to combine basic selectors to create more specific rules. Compound selectors help you target elements that meet multiple criteria and reuse existing styles to create new ones—all without duplicating code. Enjoy! 🎉

Five CSS Selectors That Every Developer Should Know!

CSS just got more powerful, and so can you! Dive into this latest article where we unpack the :has() selector, showcasing how it can elevate your web designs with practical, real-world examples. 🌟

LinkedIn - https://www.linkedin.com/company/skillivo/posts/?feedView=all

Website- https://skillivo.in/has-selector-in-css/

✔️ What is the :has() Selector?

✔️ Key Features

✔️ Highlight Parent Element using :has selector

✔️ Highlight Form field using :has selector

✔️ Styled list with specific elements using :has selector

✔️ Interactive Shopping Cart using :has Selector

✔️ Interactive Profile Card using :has Selector

✔️ Parent Highlight on Child Focus using :has Selector

✔️ Stylish and Functional Navigation Menu using :has Selector

✔ Theme Chooser using :has Selector

✔️ Five Star Rating with :has Selector

✔ Benefits of Using :has() :

Introduction

Welcome to the world of web development, where CSS selectors play a crucial role in shaping the visual presentation of a website. As a developer, understanding how to find and utilize CSS selectors efficiently can significantly enhance your ability to style and design web pages. In this guide, we'll delve into the intricacies of locating CSS selectors, with a particular focus on using the powerful tools provided by the Chrome Developer Tools. Whether you're a seasoned developer looking to brush up on your skills or a beginner eager to grasp the fundamentals, this exploration will equip you with valuable insights and techniques to navigate the world of CSS selectors with confidence.

Understanding CSS Selectors

Before we dive into the specifics of finding CSS selectors, it's essential to grasp the fundamental concepts that underlie these powerful tools. CSS selectors are patterns used to select and style HTML elements on a web page. They allow developers to target specific elements based on their attributes, relationships, and positions within the HTML document. Here's a breakdown of key concepts to enhance your understanding: - Simple Selectors: These are the basic building blocks of CSS selectors. They target elements based on their tag name, class, or ID. For example, p selects all paragraphs, .class selects elements with a specific class, and #id selects an element with a particular ID. - Combinators: Combinators are used to define relationships between different elements. The most common ones include the descendant combinator (space), the child combinator (>), and the adjacent sibling combinator (+). - Attribute Selectors: These selectors target elements based on their attributes, such as . This provides a flexible way to style elements with specific characteristics. - Pseudo-Classes and Pseudo-Elements: Pseudo-classes allow you to style elements based on their state, such as :hover for mouse hover. Pseudo-elements target specific parts of an element, like ::before and ::after. Understanding these foundational concepts lays the groundwork for effectively using CSS selectors in your projects. As you explore the world of web development, keep in mind that CSS selectors offer a versatile and powerful means to apply styles selectively, providing the fine-grained control needed to create visually appealing and responsive web designs.

Inspecting Elements in Chrome

Chrome Developer Tools is an invaluable resource for web developers, offering a suite of features to analyze and manipulate web pages. Inspecting elements is a fundamental aspect of this toolkit, allowing developers to explore the HTML and CSS structure of a webpage in real-time. Here's a comprehensive guide on inspecting elements in Chrome: - Opening Chrome Developer Tools: To begin inspecting elements, right-click on the webpage element you want to examine and select "Inspect" from the context menu. Alternatively, you can press Ctrl+Shift+I (Windows/Linux) or Cmd+Opt+I (Mac). - Elements Panel: The "Elements" panel is where you can view and manipulate the HTML and CSS of the selected element. It provides a hierarchical representation of the document's structure. - Styles Panel: Within the "Elements" panel, the "Styles" panel displays the applied styles for the selected element. You can experiment with styles in real-time, making it a valuable tool for debugging and refining your design. - Console: The "Console" tab is where you can interact with the page using JavaScript. It's a powerful tool for debugging and testing snippets of code. - Network Panel: For analyzing network activity, the "Network" panel is crucial. It provides insights into resource loading times, helping you optimize page performance. Additionally, Chrome Developer Tools offers advanced features such as breakpoints, network throttling, and emulation of various devices for responsive design testing. PanelPurposeElementsInspect and manipulate HTML and CSSStylesView and modify applied stylesConsoleInteract with the page using JavaScriptNetworkAnalyze network activity By mastering the art of inspecting elements in Chrome, developers can streamline their workflow, diagnose issues, and gain a deeper understanding of the structure and styling of web pages.

Finding CSS Selectors

Locating the right CSS selectors is a pivotal skill for developers, influencing the precision and efficiency of styling in web development. In this section, we'll explore various techniques and tools available in Chrome Developer Tools to assist in finding CSS selectors effectively. - Inspector Tool: The Inspector tool in Chrome Developer Tools allows you to hover over elements on a webpage and reveals the corresponding HTML and CSS. This visual aid is invaluable for identifying the structure of a page and determining the appropriate selectors. - Element Selection: By right-clicking on an element in the "Elements" panel and choosing "Copy" > "Copy selector," you can copy the unique CSS selector for that specific element. This method ensures accuracy and eliminates the guesswork associated with writing selectors. - Console Commands: The Console tab in Chrome Developer Tools enables you to experiment with JavaScript and provides dynamic ways to find CSS selectors. For instance, you can use document.querySelector() to test and retrieve a selector for a particular element. - Search Functionality: The "Find" tool in the "Elements" panel allows you to search for specific elements or text within the HTML. This can be particularly useful when dealing with larger codebases or intricate document structures. - Computed Styles: The "Computed" tab in the "Styles" panel displays the computed styles for an element, including the applied CSS rules. This aids in understanding how styles are inherited and computed, assisting in the refinement of selectors. Developers often encounter challenges in selecting elements with complex structures or dynamic content. In such cases, combining CSS selectors intelligently or using more advanced selectors becomes essential. SelectorPurpose:nth-child()Selects elements based on their position within a parent.:not()Excludes elements that match a specified selector.Selects elements with an attribute that starts with a specific value. By mastering these techniques and leveraging the power of Chrome Developer Tools, developers can navigate the intricacies of web development with precision and ease, ensuring their CSS selectors target the right elements every time.

Common Challenges

While working with CSS selectors in web development, developers often encounter various challenges that can impact the styling and layout of a webpage. Understanding and overcoming these challenges is essential for creating robust and visually appealing designs. Here are some common challenges and strategies to address them: - Specificity Issues: One challenge arises when multiple CSS rules compete for styling the same element. Understanding specificity—how browsers prioritize styles based on selector types—helps in resolving conflicts and ensuring the intended styles are applied. - Dynamic Content: Websites with dynamic content, especially those relying on JavaScript frameworks, pose a challenge in terms of selecting elements that may not exist in the initial HTML. Using event delegation and understanding the Document Object Model (DOM) is crucial to addressing this challenge. - Cross-browser Compatibility: Different browsers may interpret CSS rules differently, leading to inconsistencies in styling. Testing and utilizing vendor prefixes where necessary can help achieve a consistent look across various browsers. - Performance Impact: Inefficient or overly complex CSS selectors can impact page loading times. Optimizing selectors and minimizing the use of universal selectors contribute to a more performant website. - Responsive Design: Crafting selectors that adapt to different screen sizes and devices is vital for responsive design. Media queries and relative units, such as percentages and ems, play a key role in creating designs that scale seamlessly. Addressing these challenges requires a combination of best practices, a deep understanding of the document structure, and proficiency in using advanced CSS features. Furthermore, staying informed about updates and changes in web standards ensures developers are equipped to handle evolving challenges in the dynamic landscape of web development. ChallengeStrategySpecificity IssuesUse more specific selectors or refactor styles to avoid conflicts.Dynamic ContentEmploy event delegation and understand the DOM for dynamically generated elements.Cross-browser CompatibilityTest across multiple browsers and use vendor prefixes when needed.Performance ImpactOptimize selectors and minimize the use of universal selectors for improved performance.Responsive DesignImplement media queries and use relative units for adaptable designs. By proactively addressing these challenges, developers can enhance the resilience and effectiveness of their CSS selectors, contributing to a smoother and more reliable web development experience.

Best Practices

Mastering CSS selectors involves not only understanding the syntax and techniques but also adopting best practices that contribute to maintainable, efficient, and scalable code. Incorporating these best practices into your workflow ensures a smoother development process and promotes a consistent and polished user experience. Here are some key best practices for working with CSS selectors: - Keep Selectors Simple: Whenever possible, favor simple and concise selectors over complex ones. This enhances readability and makes it easier to understand and maintain your stylesheets. - Use IDs and Classes Wisely: Strike a balance between using IDs and classes. While IDs should be reserved for unique elements, classes are suitable for styling groups of elements. Avoid excessive reliance on IDs for styling, as it can lead to specificity issues. - Avoid !important: While it may seem like a quick fix, the use of !important in CSS can lead to specificity conflicts and make it challenging to debug styles. It's generally better to refactor your styles for better specificity. - Organize Stylesheets: Maintain a clear and organized structure in your stylesheets. Group related styles together and consider using modular approaches, such as BEM (Block, Element, Modifier) methodology, to create more maintainable and scalable code. - Comment Strategically: Add comments to your CSS code to explain complex or non-intuitive parts. However, avoid excessive commenting, as it can clutter the code and make it harder to read. Furthermore, incorporating a naming convention for classes and IDs, such as lowercase with hyphens or camelCase, promotes consistency across your codebase. ConventionExampleLowercase with Hyphensmy-class-nameCamelCasemyClassName Finally, stay informed about the latest CSS features and best practices to ensure your skills remain current in the ever-evolving landscape of web development. Adopting these best practices not only improves the quality of your code but also enhances collaboration and maintainability in larger development teams.

FAQ

Explore answers to frequently asked questions about finding CSS selectors in Chrome and enhancing your web development skills: Q: Why is it important to master CSS selectors? A: CSS selectors are fundamental to styling web pages. Mastering them provides precise control over the appearance of elements, leading to more polished and visually appealing designs. Q: How can I find CSS selectors using Chrome Developer Tools? A: Utilize the "Inspector" tool in Chrome Developer Tools to hover over elements and inspect their HTML and CSS. Additionally, use the "Copy selector" feature to obtain the unique CSS selector for a specific element. Q: What are some common challenges when working with CSS selectors? A: Common challenges include specificity issues, dealing with dynamic content, ensuring cross-browser compatibility, addressing performance impacts, and creating responsive designs. Understanding these challenges is crucial for effective problem-solving in web development. Q: Are there advanced CSS selectors I should be aware of? A: Yes, advanced selectors like :nth-child(), :not(), and attribute selectors () provide powerful ways to target specific elements based on their position or attributes. Q: What are some best practices for working with CSS selectors? A: Best practices include keeping selectors simple, using IDs and classes judiciously, avoiding the use of !important, organizing stylesheets, and commenting strategically. Adhering to naming conventions for classes and IDs also contributes to code consistency. Feel free to refer to these FAQs as you navigate the intricacies of CSS selectors in Chrome and elevate your web development expertise.

Conclusion

Introduction

Welcome to our comprehensive guide on using CSS Selectors in Selenium, tailored for programmers and web automation enthusiasts. CSS selectors play a pivotal role in Selenium automation testing by enabling you to locate and interact with web elements on a page. This guide will walk you through the fundamental concepts, best practices, and practical examples of harnessing CSS selectors in Selenium, empowering you to take your automation skills to the next level.

Understanding CSS Selectors

Cascading Style Sheets (CSS) selectors are a fundamental part of web development, allowing you to define the presentation and styling of HTML elements on a web page. In the context of Selenium, CSS selectors are powerful tools used to locate specific web elements for automation testing. To effectively use CSS selectors in Selenium, it's crucial to grasp their basics and types. Here's a detailed breakdown:

1. What are CSS Selectors? CSS selectors are patterns that define how to select HTML elements for styling. They specify which elements should be affected by the CSS rules. In the realm of Selenium, CSS selectors help identify elements on a web page so that automation scripts can interact with them. Key aspects to understand include: - Patterns: CSS selectors use patterns to match specific HTML elements based on their attributes, such as class, ID, tag name, and more. - Specificity: Selectors can be very specific, targeting one element, or more general, affecting multiple elements on a page. - Priority: CSS selectors follow a specific order of priority, with more specific selectors taking precedence over general ones. 2. Types of CSS Selectors CSS selectors come in various types, each designed for different scenarios and requirements. When using Selenium for web automation, you'll encounter the following types: Selector TypeDescriptionTag SelectorsSelect elements based on their HTML tag, e.g., or .ID SelectorsSelect elements by their unique "id" attribute, ensuring precision.Class SelectorsSelect elements with a specific class attribute, allowing you to style or interact with a group of elements.Attribute SelectorsTarget elements based on their attributes like "href," "src," or custom data attributes.Pseudo-ClassesUse pseudo-classes to select elements in specific states, such as ":hover" or ":nth-child(2)." These are handy for simulating user interactions. Understanding the various selector types and when to use them is essential for crafting effective and efficient CSS selectors for Selenium automation. As we proceed, we will delve deeper into practical examples and best practices for using these selectors to enhance your web automation testing skills.

Using CSS Selectors in Selenium

Now that you have a solid understanding of CSS selectors, it's time to dive into how to utilize them effectively in Selenium for web automation. We'll explore the essential steps, practical examples, and best practices to empower you in automating web interactions with precision and reliability. 1. Setting Up Selenium Before you can use CSS selectors in Selenium, you need to set up the Selenium WebDriver and configure your development environment. Here's a high-level overview of the steps: - Install Selenium WebDriver: Start by installing the Selenium WebDriver for your programming language of choice, such as Java, Python, or C#. You can usually do this through package managers like Maven or pip. - WebDriver Configuration: Configure the WebDriver to use a specific web browser like Chrome, Firefox, or Edge. You'll also need to specify the browser's path on your system. - Download Web Driver Executable: For each browser, you'll need to download the respective WebDriver executable and specify its location in your project. - Initialize WebDriver: In your code, initialize the WebDriver, which will allow you to control the browser during automation. 2. Locating Elements with CSS Selectors Once your Selenium setup is in place, you can start using CSS selectors to locate and interact with elements on a web page. This is a crucial part of web automation testing. Here's a breakdown of how it works: - Find Element: Use WebDriver's built-in method to find an HTML element using a CSS selector. For example, you can use driver.findElement(By.cssSelector("your-selector")). - Perform Actions: After locating the element, you can perform various actions such as clicking, typing, or checking its properties. These actions simulate user interactions with the web page. 3. CSS Selector Examples To provide a better understanding, let's walk through some practical CSS selector examples that you may encounter during web automation testing. We'll illustrate the usage of various selector types: Python# Import the Selenium WebDriver from selenium import webdriver # Initialize the Chrome WebDriver driver = webdriver.Chrome() # Navigate to a website driver.get("https://example.com") # Find an element by CSS selector and interact with it element = driver.find_element_by_css_selector("input") element.send_keys("your_username") # Find another element by CSS selector and interact with it submit_button = driver.find_element_by_css_selector("button") submit_button.click() # Close the browser driver.quit() Selector TypeExampleTag Selectordriver.findElement(By.cssSelector("button")) - Locates all elements on the page.ID Selectordriver.findElement(By.cssSelector("#elementId")) - Finds the element with the specified ID attribute.Class Selectordriver.findElement(By.cssSelector(".button-class")) - Targets all elements with the given class name. These examples showcase how to use CSS selectors in practical scenarios. By applying these techniques, you can automate interactions with web elements efficiently and accurately, making your Selenium tests robust and reliable. Throughout this section, we've covered the fundamental steps for setting up Selenium, locating elements with CSS selectors, and provided practical examples of using different selector types. In the upcoming sections, we'll explore best practices, tips, and FAQs to further enhance your knowledge of using CSS selectors in Selenium automation testing.

Best Practices and Tips

When using CSS selectors in Selenium for web automation, following best practices and adhering to essential tips is crucial for writing efficient, robust, and maintainable automation scripts. Let's explore the key guidelines that will enhance your Selenium test suite: 1. Selector Specificity Choose the Right Selector Type: To ensure that your automation script is robust, select the most appropriate CSS selector type. For example, use ID selectors for unique elements and class selectors for multiple elements sharing a common attribute. Avoid overusing complex selectors, which can lead to fragile tests. 2. Avoid Hardcoding Selectors Parameterize Selectors: Instead of hardcoding selectors directly in your code, use variables or configuration files to store them. This makes it easier to update selectors without modifying your codebase, enhancing maintainability. 3. Prioritize ID and Name Attributes ID and Name Attributes: Whenever possible, prefer using the "id" and "name" attributes in your CSS selectors. These attributes are usually unique and provide a direct way to identify elements. 4. Use Relative Selectors Relative Selectors: Leverage relative selectors to navigate from known elements to the target element. For example, use CSS selectors to find a parent element first and then locate the desired child element within it. This approach adds flexibility to your tests. 5. Handling Dynamic Elements Coping with Dynamic Elements: Websites often contain elements with dynamic attributes or structures. Be prepared to handle these changes by using CSS selectors that can adapt to dynamic scenarios. Pseudo-classes like ":nth-child" and ":contains" can be helpful in such cases. 6. Regular Expression (Regex) Selectors Regex Selectors: Selenium supports regular expressions in CSS selectors. You can use "^" to indicate starts with and "$" to indicate ends with, allowing you to create more flexible selectors that match dynamic attributes. 7. Test Data Separation Separate Test Data: Keep your test data separate from your CSS selectors. This separation improves script maintainability and allows you to reuse selectors for different test data scenarios. 8. Browser Compatibility Verify Cross-Browser Compatibility: Ensure that your CSS selectors work consistently across different web browsers. Selenium supports multiple browsers, so it's essential to test your scripts on all target browsers to catch any compatibility issues. 9. Regular Maintenance Regularly Review and Update Selectors: As web applications evolve, selectors may become outdated. Periodically review and update your CSS selectors to accommodate changes in the web page structure. 10. Exception Handling Implement Error Handling: Incorporate robust exception handling in your scripts. This ensures that if a selector fails to locate an element, your script can gracefully handle the situation and report the error without crashing. By following these best practices and tips, you'll be well-prepared to create Selenium automation scripts that are reliable, maintainable, and adaptable to the dynamic nature of web applications. This will help you achieve efficient and effective web testing with CSS selectors in Selenium. Websites for free HTML & CSS templates:◉ uideck - https://t.co/CwFDNG2tCg◉ free-css - https://t.co/whAWPtPsiR◉ splawr .com - https://t.co/0wGOimKzBD◉ onepagelove - https://t.co/3OoqGpTq2K◉ tooplate - https://t.co/HhPldbSsrd◉ nicepage- https://t.co/gL8CrjVSGc… pic.twitter.com/rMNNdQO5bc— Rizwan (@mdrizwanalam72) November 4, 2023

FAQ

As you delve into the world of using CSS selectors in Selenium for web automation, you might have some questions and concerns. Here are answers to common frequently asked questions to help you navigate through this process: Q1: What are the advantages of using CSS selectors in Selenium? A1: CSS selectors provide a powerful way to locate and interact with web elements, making your Selenium tests more efficient and reliable. They are versatile and can be used to target elements based on various attributes, such as class, ID, or tag name. Q2: Are CSS selectors the only way to locate elements in Selenium? A2: No, Selenium provides multiple methods to locate elements, including CSS selectors, XPath, and others. The choice of method depends on your specific testing requirements and the structure of the web page. Q3: What happens if a CSS selector fails to locate an element? A3: If a CSS selector cannot find the specified element, Selenium will throw a "NoSuchElementException." It's important to implement error handling to gracefully deal with such situations in your scripts. Q4: How do I handle dynamic elements with CSS selectors? A4: Dynamic elements with changing attributes can be challenging. To handle them, consider using regular expressions (regex) in your selectors or pseudo-classes like ":contains" to target elements based on their text content. Q5: Can I use CSS selectors to locate elements in iframes or frames? A5: Yes, you can use CSS selectors to locate elements within iframes or frames. However, you need to switch to the frame using Selenium's frame-switching methods before using the CSS selector to locate elements inside the frame. Q6: What should I do if a web page's structure changes, and my selectors become obsolete? A6: Web applications evolve, and elements may change. It's essential to regularly review and update your selectors to adapt to these changes. Proper error handling can also help you identify issues and make necessary updates. Q7: Is there a tool to test and validate CSS selectors before using them in Selenium? A7: Yes, there are online CSS selector testing tools that allow you to test and validate your selectors against a given HTML structure. These tools can help you verify the accuracy of your selectors before implementing them in your scripts. These frequently asked questions and answers provide insights into some common queries that may arise as you work with CSS selectors in Selenium for web automation. If you have additional questions, feel free to ask or refer to the Selenium documentation for further guidance.

Conclusion

For style purposes, the HTML element(s) are chosen using a CSS selector. HTML elements are chosen using CSS selectors based on their id, class, type, attribute, etc. The component of a CSS ruleset known as a selector really chooses the content you wish to style. Below is a list of various CSS selectors kinds.

Universal Selector

Similar to a wildcard character, the universal selector selects every element on a page. The styles offered in the example will be applied to every element on the page. * { color: "green"; font-size: 20px; line-height: 25px; }

Element Type Selector

This selector matches one or more identical HTML elements. The provided styles in the example will be applied to each and every ul element on the page. ul { line-style: none; border: solid 1px #ccc; }

ID Selector

Any HTML element that has an ID property with the same value as the selector is matched by this selector. In the example presented, all elements on the page that have ID as a container will have the provided styles applied to them. #container { width: 960px; margin: 0 auto; }

Class Selector

All elements on the page whose class property is set to the same value as the class are also matched by the class selector. In the example supplied, all elements on the page with ID box will have the provided styles applied to them. .box { padding: 10px; margin: 10px; width: 240px; }

Descendant Combinator

You can combine two or more selectors using the descendant selector, or more precisely, the descendant combinator, to make your selection process more precise. #container .box { float: left; padding-bottom: 15px; } All elements with a class of box that is inside an element with an ID of the container will be affected by this declaration block. It's important to remember that the .box element doesn't have to have a direct child in order for the styles to be applied; there might be another element wrapping the .box element.

Child Combinator

Similar to a selector that employs a descendant combinator, a selector that utilizes the child combinator only targets immediate child items. #container> .box { float: left; padding-bottom: 15px; } All elements that have the class of box and are direct children of the #container element will be matched by the selection. That implies that there cannot be another element wrapping, unlike the descendant combinator. It must be a direct child element of box.

General Sibling Combinator

A selection that compares components based on their sibling relationships using a general sibling combinator. In the HTML, the chosen elements are next to one another. h2 ~ p { margin-bottom: 20px; }

Title

Paragraph example. Paragraph example. Paragraph example. Paragraph example. All paragraph elements ) in this example will be styled according to the given rules, but only if they are siblings of

elements. The styles would still be in effect if there were other items between the

and

Adjacent Sibling Combinator

The plus sign (+) designates a selector that employs the adjacent sibling combinator, which is nearly identical to the general sibling selector. The targeted element must be an immediate sibling rather than a general sibling, which is the distinction. p + p { text-indent: 1.Sem; margin-bottom: 0; }

Title

Paragraph example. Paragraph example. Paragraph example. Paragraph example. Paragraph example. The paragraph elements in the aforementioned example that immediately follow other paragraph elements will be the only ones to receive the given styles. This implies that these styles would not be applied to the page's initial paragraph element. Additionally, the styles wouldn't be applied to the second paragraph in a pair if another element appeared in between them.

Attribute Selector

Cascade - Just Like a Waterfall

Like everyone who begins to learn coding for front-end development, I started off by learning some basic HTML. And like - I would guess - most people, I thought it was quite straightforward and found it incredibly satisfying to see a page develop in front of my eyes while I was inputting tags and elements in my code editor. 

But then came CSS - Cascading Style Sheet. It made sense to me that we need to create a separate style sheet in our editor that we then link to our HTML pages, to make sure that we keep the content (created through HTML) neatly separated from layout, looks and style (created through CSS). What I did not understand, however, was what the C stands for.

One of the definitions of cascade that Merriam Webster offers apart from “a steep usually small waterfall” is:

“ something arranged or occurring in a series or in a succession of stages so that each stage derives from or acts upon the product of the preceding” 

Looking back at the mistakes I made while trying to implement CSS - mistakes I absolutely could not understand, and which seemed completely random to me - now make a lot more sense. Cascading means there is a certain succession, and the order in which we write rules onto our style sheets is important. 

Just like the flow of a waterfall: we need to create our style sheets from top to bottom. Image by  sgcdesignco on unsplash.

Once I understood one needs to follow a certain order, I also understood why some of the things I had input were suddenly overruled by others. Shay Howe’s Website Learn to Code HTML and CSS perfectly breaks this down:

p {  background: orange;  font-size: 24px; } p {  background: green; }

“ Because the paragraph selector that sets the background color to green comes after the paragraph selector that sets the background color to orange, it will take precedence in the cascade. All of the paragraphs will appear with a green background.”

Thanks to Shay Howe, I also finally understood the different kinds of selectors we are working with in CSS - type selectors, class selectors and id selectors - and that these selectors have a different specificity, and consequently a different weight in the cascade. 

Type selectors such as <p> (paragraph) or <div> (dividers) select elements according to their type. They are quite broad.

Class selectors are more specific, they allow us to target elements according to their class attributes. They can be used several times throughout a page. The example Howe uses here is

CSS

.awesome { ... }

HTML

<div class="awesome">...</div> <p class="awesome">...</p>

What became clear to me through his examples is that I as the developer can come up with my own class attributes (as seen in .awesome). Before, I had always thought that there are a number of attributes one needs to choose from. But in fact, I have complete creative freedom over the choice of my attributes.

Id Selectors are even more specific than class selectors. They are unique and can only be used one single time. 

CSS

#shayhowe { ... }

HTML

<div id="shayhowe">...</div>

Just like the class attributes, I as the developer can come up with my own id attributes. And most importantly to note: there more specific a selector is, the more weight it carries, which means it receives precedence in the cascade. 

Combining Selectors: Just like German Compound Words

One of the most relevant things I learned from Howe’s  Learn to Code HTML and CSS is that you can combine selectors and thus be more specific and detailed. To understand the logic behind this, it helped me to draw the analogy to German compound words.

The German language is famous for producing extremely long words, because it can simply “glue” words together to express something very specific. In English, for example, those words would often be separated by “of” or “by” or “from.”

Confusing? Maybe. But looking only at the very last word of this compound, we know this is just a very specific kind of Barbier, a barber.

To give a simple example:

Blume = flower; Topf = pot; Erde = soil; Dünger = fertilizer

Blumentopf= flower pot. It is a specific pot used for flowers. Topf (or pot) is the main qualifier.

Blumentopferde = a specific kind of soil that is used for flowers in a pot. Erde (soil) is the main qualifier. 

Blumentopferdendünger = a specific kind of fertilizer that is used for soil that is used for flowers in a pot. Dünger is the main qualifier. 

From this example we can see that the word at the end (or at the very right) is always the main qualifier. The words preceding just give extra information, and add specificity. 

With regard to selectors in CSS, it seems to work the same way. Again, an example taken from Howe: the goal is to make the background of only one specific paragraph yellow amidst an otherwise completely brown-coloured block of paragraphs(the <p>s inside the <div>):

HTML

<div class="hotdog">

 <p>...</p>  <p>...</p>  <p class="mustard">...</p> </div>

CSS

.hotdog p {  background: brown; } .hotdog p.mustard {  background: yellow; }

The combination of several selectors .hotdog p.mustard allows us to target only one specific paragraph without affecting the others. Like the German compound words, we need to read from right to left. The selector at the very right is the key selector, all the others to the left are prequalifies. Like the Barbier and the Dünger are just a very specific kind of barber and fertilizer, the .mustard selector is a very specific kind of selector that can be found inside the p selector that can be found inside the .hotdog selector.