CSS Lint is harmful
In short: don’t blindly follow the crap these tools tell you. Chances are very high you’ll do yourself more harm than good, ending up with harder to maintain, bloated code, with nary a change in how fast your site feels.
more on mattwilcox.net
A detailed critique of CSS Lint. The content is worth reading, but it would benefit from less offensive (if not obnoxious) tone. There's an interesting response that deals with one misconception from the above article, that ID's are significantly faster than classes.
