I've been fighting for some time to come up with a layout that really genuinely works. I want to use CSS and end up doing strict XHTML, so I'm working towards that end mostly by trying to eliminate all tables.
The solution finally came from A List Apart in the form of Creating Liquid Layouts with Negative Margins. This method allows you to create a simple, CSS-based layout that will not break all over the place when content ends up being wider than the div#content (or similar.) I have implemented it as a two-column design as I am not really interested in a right sidebar, which I think is for morons. A lot of web users are still using an 800x600 display and you end up with this tiny little gutter for content if you have three columns. The site is about content, right? If it's about sidebars, it must be pretty boring.
For the moment I've abandoned sIFR, but I plan to come back to it when I have a little bit of time. Regardless, enjoy my poorly-validating webpage. (Most drupal modules produce absolutely atrocious code, and I may have some errors of my own in this initial rework of my theme.