Developers using the YUI Grids CSS system may notice that the common 25%/50%/25% layout is not documented nor supported by the YUI Grids builder tool. Following is a solution using nested grids that achieves this layout (nearly, but not pixel-perfect).
This code has been tested within a custom doc size (980px) in Firefox 2 and on IE 6. With a page constrained at 980 pixels in width, we end up with:
233px WEST | 22px gutter | 472px CENTER | 18px gutter | 235px EAST
Not pixel-perfect, but close...and still adhering to YUI standard markup with no additional CSS required.