What’s returned when using list_cat?

I want to use three category and two pages for my navigation. I’ve inserted the two wp call to list categories and list pages in the header.
It lists the links correctly.
I’m using css to create a custom theme and have styled the list to look like tabs. Problem is:
How do I change the css to correspond to the active link? I know the list_cat returns a variable that you can use in the css (that is, it sets the class of the li tag)…
1. Is there something like that for Pages, so I know which is the current page?
2. I have seen the exclude argument for the list_cat category function call- is there something I can use to call only three (instead of having to exclude all others and new ones down the road)?

thanks!
Ron