where can I read the default style's CSS?

[Attitude5ire]

This is the main css.. whatever you declare here should pretty much be global unless u have extra addons which add diff. css with same class.
You can pretty much define whatever you want. no matter what changes happen i thought you asked about button. Not sure how rollover is related to it but just post maybe what you are trying with ur css and etc. maybe i can give a better solution for u