Peter Dominic Ryan wrote up a nice entry over at the Real Mac forums for how to use CSS with sitemap:



I think the best way to approach CSS and your SiteMap is the way it is done in the rW Toolbar. The toolbar is just made up of nested unordered lists <ul><li><ul>...</ul>, and these are wrapped with a unique <div>. If you study the style sheet you will see the declarations are pretty much like the following:


Code:
#navcontainer ul {…}
#navcontainer ul li {…}
#navcontainer ul li a {…}
#navcontainer ul ul {…}
#navcontainer ul ul li {…}
#navcontainer ul ul li a {…}
#navcontainer ul ul ul {…}
#navcontainer ul ul ul li {…}
#navcontainer ul ul ul li a {…}

Simply take the same approach with SiteMap, but this time it is wrapped with the following:



Code:
<div id="sitemap"> … </div>
So, for each tag you want to style differently, you just make it a descendant selector of this <div>. As an example only, say your sitemap has three levels in its hierarchy, well the following selectors (with declarations ommitted for brevity) would do a nice starting job:
Code:
#sitemap ul { … }
#sitemap ul li { … }
#sitemap ul li a { … }
#sitemap ul ul { … }
#sitemap ul ul li { … }
#sitemap ul ul li a { … }
#sitemap ul ul ul { … }
#sitemap ul ul ul li { … }
#sitemap ul ul ul li a { … }




As I said above, take the toolbar as an example of how to approach this, and before you get stuck into the CSS, take a good look at the output markup of your SiteMap page for clues on how to best approach it.