alt131 - 5:15 pm on Aug 13, 2011 (gmt 0)
Hi valanews, and welcome to WebmasterWorld :)
Good on you for bothering to validate - and I think you've raised the really good issue that this sort of code is seen so often it has become "normal". To my mind this is a situations where "what is commonly used" is not the same as "best practise".
what is the wrong? I think that css code is normal!
Recall the validator checks for whether code is valid - not whether it is efficient, or even "necessary" as explained by Paul and Lucy. There are many reasons code ends up being overqualified in this way, and as Paul has referred, often caused by not coding to take full advantage of the "cascade" and "specificity". That doesn't mean the code is "wrong" - but it does mean the code is far less efficient than it could be. Given one aim of code is to deliver content to users as efficiently as possible, it makes sense to give that some priority.
Both make sense to me ;)
I think I just made that sound more complicated than it is "If you've only got one of something, it doesn't need a class."