question about CSS styling

I wonder if you can point me in the right direction on CSS styling.

I have many inherited values from my theme (e.g.,
<li>). So it’s not clear, for example, how to style the category title when displaying categorised posts. In firebug I can see it wrapped in <h3> tags. How would I style this individually for the sitemap output without changing that value across my whole site?

As another example, I’d like to play with the positioning and style of the date, when dates are added to the posts output. It’s not clear how I can do that, because it doesn’t seem to have its own CSS ID.

Thanks for any pointers.

Love the plugin, by the way.
http://ww.wp.xz.cn/extend/plugins/wp-realtime-sitemap/