I have done alot with my css so I dont think line 897 would be correct. Was trying to figure out wat id to use or if the are different psuedo for doing this.
like mark mentioned, user.css
and the category box has id of "join_category", so you would target #join_category { .... }
Tip: Right click on the element you want to inspect -> inspect element
That not only shows you the html source so you know what id, class, whatever an element has, but also shows you linked css rules to that element
Very useful for testing