I use this css code:
Our experts are all jumping around waiting to help you but you'll need to give us a little more information to go on than that.:)
There is nothing wrong with the rule above and I can guarantee that if it was applied to a block element it would work fine on its own.
However we need the context that it is being used in and the html that goes with it and any styles that may be cascading into it also. A link would be better if available.
Only then will you get your serious help