CSS stands for Cascading Style Sheets and the "Cascading" part is what causes confusion most of the time. The key thing to remember is that the final style that is applied to elements on a page is an *aggregation* of all the attributes defined for that style in each stylesheet and "style" attribute defined on the page, with the "nearest" defined attribute taking precedence. For example:

A.css has class .MyStyle { color: red; font-size: 10pt }
B.css has class .MyStyle { font-weight: bold }
C.css has class .MyStyle { font-size: 8pt }

and an element is defined like this: <div class="MyStyle" style="font-size: 9pt"> blah </div>

In this example, the final style that will be applied to the div element is { color: red; font-weight: bold; font-size: 9pt }   PLUS any other style attributes defined in elements that are parents of the div.

The easiest way to determine the order of stylesheets in DNN is to View Source for the rendered page and look at the <LINK> tags in the head. The order in which the stylesheets appear is the order of precedence.

As a personal preference, I make every .css file other than skin.css blank. Other people use different approaches, but this works for me.

Without a doubt, the most useful resource I could recommend is the O'Reilly CSS Pocket Reference. This mini-book is concise, accurate and way faster than even Googling when you need to look up a CSS attribute. My computer has my mouse on the right, and a well-thumbed O'Reilly reference on the left. http://www.amazon.com/gp/product/0596007779/104-2374996-3424721?v=glance&n=283155 ... best $10 you will ever spend.

Nik

Nik's right - a good CSS book really goes a long way - I've got quite a few and am still learning all the time. There are some online references, but nothing beats printed matter some of the time.

If you are after a little information on how to understand the hierachy of the CSS files - then I've explained in a little more detail on this post -

http://forums.asp.net/1160138/ShowPost.aspx

You an also assign your own classes to overcome things not looking quite like you want.

This is a little more food for thought on the post.

Nina Meiers