Most of the time, i build sites up that will look nice in a text browser. (Lynx)*
Then i will add some basic layout to make it look nice, add a little style.
Done, for the old browsers, they are left behind, no wasting time any more.
Now a second stylesheet using the @import method will add more advanced CSS.
* This is also good for the sake of optimizing your page for web crawlers.
Good ol' SEO.