Hardcore what?! Nope, it really is codeMDASHnothing as exciting as you were hoping for. This is just a useful little tip that can trim five bytes off of every absolute link in your documents. This might not sound like a lot at all, but over a large enough site this can amount to quite a bit, and it’s alarmingly simple.
Take the following hyperlink: <a href="http://google.com/">Google</a>. That is an absolute link to Google’s homepage. However you can safely lose five bytes from that…
The following will work in exactly the same way: <a href="//google.com/">Google</a>. That will take you to the same place as beforeMDASHGoogle’s homepage.
This not only works on the href attribute, but also on the src attribute too. In fact, anywhere where you’d normally use http://... you can now use //... as they both resolve to the same thing.
Wes Mason, colleague, has since pointed out that this simply uses the same protocol as the current abURL, therefore if you’re linking from a http:// domain to a https:// domain you will need to explicitly define that in the link, //... won’t work in this instance.