I haven't tried viewing my site in 1600x1200, in what ways does the code not cope?
I haven't heard of SE so I can't comment on that. Howerver, I would assume that the vast majority of sites do not show up well in text/aural browsers (especially ones made in flash...)
If I were going to optimise the site for all browsers, how would I go about doing so?
Oh, and when I said 'average user', I was referring to the people who use IE/Netscape/Mozilla on a decent computer (PC or Mac).