I'm on the fence of about keeping the question undeleted with historical lock. On the one hand, there is some good content that may be worth keeping. On the other hand, the information is/has already rapidly become out of date. Your own comment on the top answer is a perfect example of this:
do not @import if you don't have to, and for the love of god do not use CSS frameworks – Jason Oct 13 '10 at 22:16
@Jason: Really, do not use Bootstrap or Foundation? – Dan Dascalescu Mar 21 at 9:31
Do you realize you're replying to a two year old comment, made at a time when Bootstrap and Foundation did not exist? If you look around, some of the answers are already out of date, are subjective (Should you use a framework? Which CSS reset to use? And which of these 'tips and tricks' are for 'beginners' anyway?), repeat each other, and just aren't very good.
We could keep them around, but the question would still show up on search results, frozen perpetually in the state that they were when the question is locked (not that not locking would do it any good either - the top answer should be updated with information about Firefox and Chrome's native developer tools, but in the three years since that answer was posted nobody bothered to do that). It would, in fact, be a lot like W3Schools - perpetually out of date, yet still occupying the top results on search engine rankings.
That's not to say the information is all useless - far from it. But at some point without being maintained it'll probably do more harm to keep them around then to simply delete the answer and move it somewhere where they could actually be maintained (MDN comes to mind - it shouldn't be too hard to add these information to the CSS tutorial).