skin.css should be loaded after any module.css, so you should be able to overwrite the values if you add the CSS there

I have the same exact problem. Unfortuneately, I am looking at a core DNN module (in my case the Calendar module). It gets its style from the default.css class. When you read the rules for CSS (see below), you discover that the web browser deals with cascade conflicts by assigning weight to CSS classes. The root class is known as the author class - in this case it is the default.css class in DNN. There is no reason that anyone should EVER use "!important" in a default class unless you are positive that you NEVER want anyone to be able to overwrite your default definition. Even though this hard and fast rule has changed in recent years, many web applications are, unfortunately, behind the times and impliment older CSS standards. Since that seems to be the case here, DNN default skins and CSS classes should avoid the use of "!important".

For more about assigning property values, cascading, and inheritance please reference the following web page.

www.w3.org/TR/REC-CSS2/cascade.html

The use of the "!important" argument in the default.css class tells me that the original designers aren't really up to speed on the changes in CSS and didn't really adhear to the guiding standards upon which CSS was built in the first place. The only answer I have been able to come up with is to edit the default.css file and keep a change file that I need to merge every time I upgrade. It isn't the best solution, but its a good work around until the DNN dev team can correct this oversite and once again begin adhering to the standard.

Cheers!