Forum Moderators: open
<a href="http://www.example.com/page.htm" ....
In addition there can be all kinds of javascript attributes to change visibility of various divs and so on. It's still search engine friendly as long as the urls of links themselves are not obscured in javascript code, by the use of arrays, .js defined functions, whatever.
Our library has a good thread that walks you through the "gears" of a search engine friendly menu system:
[webmasterworld.com...]