>No one ever uses less then 800x600 (pre <'98).
I do, always. I don't want to have the browser on my whole screen. Long line
are harder to read (Knuth says 66 Characters per line are optimal), and I want
to see my emacs next to the browser. But OK, most people do it differently.
Well, you will find the old theme has a similar problem too. Its just long text forcing the page to be big. Its not something I can fix. Sorry.
Can there be problems with a page becoming to wide in the future?
If no, I'd say you can leave everything as it is.
Anything above 800x600 will always work. Again, not many people use smaller than that. There is no point redoing the whole theme to work with resoulation which maybe 0.2% of the viewers use :P