Is it a really hideous sin, when you make your own WordPress template, to use an HTML table for the structure? My three-column layout works, dammit. In all browsers. Yeah, it’s old code. But it works.
All the CSS-only three-column layouts have problems with one browser or another, or are full of kludges. One freaking table, and mine flexes where I want it to flex, holds where I want it to hold, and supports even legacy browsers.