Several months ago, I noticed that the New York Times had redesigned their website to viewed by a monitor with 1024 x 768 pixels. For years I have noticed more users setting their monitors to this resolution, instead of 800 x 600, and I guess it was a matter of time before we had to reassess the lowest common factor for design of web pages in that regard.
On Monday, Jakob Nielsen wrote a piece for Alertbox stating that it is recommended to optimize web pages for that screen resolution. If Jakob says so it must be true. He talks about the need for liquid layouts, but I think once the genie is out of the bottle, stylists and designers alike will probably start making the designs fixed.