#http1.0

When the Internet Explorer setting for HTTP 1.1 is enabled on a Windows XP machine, users may have trouble connecting to some websites that still use the older Internet protocol HTTP 1.0 and get the error code 501 or "HTTP 501 Not Implemented/HTTP 505 Not Supported". To rectify this, click to clear the check box for HTTP 1.1 under the Internet Options dialog box on the advanced tab under the Tools Menu. 

HTTP 1.0 required strict "single request per connection" model, HTTP 1.1 reversed this behavior: by default, an HTTP 1.1 client and server keep the connection open, unless the client indicates otherwise (via Connection: close header).

Some key aspects to ensure:

Connection reuse: Ensure that your connection is not closed at end of each request, check header "Connection close"

Pipelining: Pipelining allows us to break the strict "send a request, wait for response" model. Instead, we can dispatch multiple requests, in parallel, over the same connection, without waiting for a response in serial fashion.