#pseudo-elements

W3C為了區分偽類及偽元素，在CSS3把偽元素的單冒號標記法改為雙冒號，但是單冒號還是有支援偽元素的判斷，是因為在CSS2跟CSS1都是統一使用單冒號。

也就是說單冒號跟雙冒號都可以，但都特地開發一個專門用來區別的標記了，還是養成使用雙冒號的習慣吧。

參考自W3C小字典

I have dynamically change position of en element which defined in CSS with :after. I tried to change it this way:

$(function(){ $('div::after').css({'top':'20px'}) })

But it doesn’t work. Is there any ways to change position?

Best Answer

You can’t. Content created by :after or :before is not part of the DOM and therefore cannot be selected or modified.

If you have a look at this example…

http://www.bennadel.com/blog/2445-Using-CSS-Pseudo-Elements-before-And-after.htm

http://www.hongkiat.com/blog/pseudo-element-before-after/