Double slash at beginning of javascript include

Question

I have been looking at the html5 boilerplate and noticed that the jquery include url starts with a double slash. The url is //ajax.googleapis.com/ajax/libs/jquery/1.5.1/jqu

Answer 1

I hate answering with a link but this explains it - http://paulirish.com/2010/the-protocol-relative-url/

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Using a protocol relative URL like "//mydomain/myresource" will ensure that the content will be served via the same scheme as the hosting page. It can make testing a bit more awkward if you ever use FILE:// and then some remote locations as they will obviously resolve back to FILE. Never the less it does resolve the mixed insecure/secure content messages you can cause by not using it.

Answer 2

So that if the .html is accessed via HTTPS; the page will not have any unsecured script.