URL of the URLs dependency protocol with double slash//start

Original: URLs-dependent protocol URL with double slash//

I wonder if you have seen the following URL notation:img URL is double slash "//" At the beginning, this notation has a special purpose, and it will determine whether the current page protocol is HTTP or HTTPS to determine the protocol of the request URL. Prevents the "This page Contains Both Secure and non-secure Items" error from appearing under IE. 

But when you browse local files, it resolves to file: // agreement. This feature can be used to load CDN:<script src= "//ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.js" ></script> also applies to css:.omgomg {Background:url (///websbestgifs.net/kittyonadolphin.gif);} Note: If you use <link> and @import to introduce CSS in IE7,IE8, two CSS files will be downloaded. Reference: http://www.paulirish.com/2010/the-protocol-relative-url/

URL of the URLs dependency protocol with double slash//start