There's an RFC for That
Too often I see colleagues developers employing Google and lurking around random results to find answers on some typical web development questions as “What does must-revalidate in Cache-Control does?”, or “Is ETag header forcing revalidation?” and similar. Usually it ends up in deciphering random answer on Stack Overflow or some other community web site.
First, of course that there is huge amount of knowledge out there and very smart people answering with deep insight on every of these questions. But still, they do present most often only their interpretation of certain clearly defined and described standard. Answers also often know to be either incomplete or plainly wrong. Second, most often these kind of responses are representing how things are implemented in certain technology, Rails for example of any other. That way usually you don’t come to the answer of
how something is done. And to grow knowledge I always tend to go deeper and understand why something is done in certain way.
Take HTTP protocol as example, it is defined in RFC2616 where everything you need to know about it is written. It has a bit unfriendly writing style, but once you get used to it you can see that it is in fact very clear and unambiguous. Other benefit of getting used to read RFC documents is that they are written in similar style and once you get used to you can benefit from vast amount of them. At the end RFC are the rules which define most of the web implementation in wide use on the net. Let the HTML5 mess aside ;)