Using various hack management techniques publicized by Doug Bowman and Molly Holzschlag, this is the default stylesheet I to in the head of my markup:

/*
        [CLIENT] screen master
*/
@import url("core.css");

/* Import WinIEx-only bugs - hide from Mac IE5 \*/
@import url("hacks.win.iex.css");
/* END hide from Mac IE5 */

/*       Import Win IE5x hacks
        ---------------------
*/

@media tty {
        i{content:"\";/*" "*/}} @import 'hacks.win.ie5.css'; /*";}
}/* */

/*       Import Mac IE5 hacks
        --------------------
*/

/*\*//*/
@import url("hacks.mac.ie5.css");
/**/

The core.css file contains my pure, "hack free" CSS. The other files referenced above contain any and all browser-specific hackery required to make IElesser browsers behave properly.