Better categories stylesheet is just a handler of the wrappers around the standard css code for the sidebox. Think of it like the Russian dolls that start out with one big doll and has one inside of it, with one inside of it, wiith one inside of it, with one....
What better categories does is control everything inside it's wrapper that IS NOT listed elseewhere. It will only change something if it is specifically called.
IE if the main stylesheet for our Russian dolls is doll.css with another called female.css and one called male.css, the dolls.css would contain all information pertinent to ALL dolls. The female.css would add things like longer hair, skirt, etc. Male would add baggy clothes, unshaven beard, beer, etc.:D
The doll wrapper would be around all dolls and a female wrapper around each doll you want to "look" female.
In this case, as happens to many folks, you're looking at the BC stylesheet and forgetting that most of this was already coverred in the main stylesheet.
If you do a CTRL-SHIFT-C you'll bring up the view of all stylesheets combined. search for category-top and you'll find wwhat's bugging you with the hover.
I know this is a bit winded but, since you're taking the time to learn, I fiurred it was time for another bit of info.
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