Member Rara Avis
Whether you use fixed width or percentages depends on the content, in my opinion.
The Passions main site uses fixed widths, designed for a typical 640x480 screen. Every cell on the main screen is a specific pixel width, forced to that width by a transparent gif, and will look almost exactly the same on every screen (okay, just a bit more squished on webTV, but not much).
The forums, on the other hands, are percentage based. Kind of. In truth, the forum screens are a mixture, with the left- and right-most columns being fixed to a specific width, and the middle column being a percentage, all nested within a single-column, 98 percent width table. Yea, it's a bit complicated. But, essentially, it's percentage based in that it will stretch to fill most of the entire screen, or shrink to fit a smaller, resized window. In spite of its elasticity, because of those fixed-width corners, the forum screens will look "about" the same regardless of screen resolution; i.e., everything on the page will appear in exactly the same spot, without any inadvertent wrapping.
I should also note that the number one reason beginners have problems with tables is because they try to mix fixed- and percentage-width columns. Do it wrong, and your tables are going to look entirely different at different resolutions, and can indeed do some really weird things. In almost every instance, the reason is because the designer is asking the browser to do something mathematically impossible. If the browser cannot do what you've asked it to do, it's going to make its own decisions - which are rarely what you had in mind.
So, why would you ever want to use a completely fixed-width screen? For the same reason newspapers and magazines use columns. Overly long lines of text are very hard on the eyes and people, being the lazy creatures we are, will usually just go find something a little easier to read. If you are displaying links like Yahoo, or short little site descriptions like Excite, or poems like we do in most of the forums, then it's not going to be too bad. But if you're publishing articles (or short stories), those really long lines of text are a hill you're asking your visitors to climb. And many of them won't.
That is one of the weaknesses of our forums, and one I hope to soon overcome.