Might I add, this is EXTREMELY useful when you're applying browser fixes to existing elements. For example, many times you need to implement a IE width fix to an element. To do this, you would apply the original style ID to the first one, and a second ID with the fix to the second one. Once this is done, you'll have a clean DIV that fixes both the first and the second.
Give this a try by using "tony's fix" on Google. It should work very well for you.