I remember when I first did some web programming, way back in 1996, people were already warning against pixel-based code. Seriously, what happened? Did people decide it's just too difficult to do percentage-based layouts?
here's yahoo's version for yui: <a href="http://developer.yahoo.com/yui/grids/builder/" rel="nofollow">http://developer.yahoo.com/yui/grids/builder/</a>