URI starting with two slashes ... how do they behave?

Lately I saw working code-blocks like this: <script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script> And according to RFC 2396 (URI Syntax) and RFC 2616 (HTTP 1.1) these URI starting with two slashes are valid, but unfortunately the RFCs don't really explain them. Can anyone point me to a resource which explains how browsers will/should/do process t

[yyamano]

“This means that when the base URI is http://a/b/c/d;p?q and you use //g, the relative reference is transformed to http://g.”

[mooz]

// (two slashes) ではじまる URI について。http か https のどちらかに展開される。