Have no absolute pixel widths for anything that isn't in pixels, that is, pictures. No absolute widths for tables, table elements, frames, or anything textual. This unfairly discriminates against people with different sized windows or fonts than you have. I realize that the smallest viewing areas are something of an inevitable problem with pictures, but you can at least minimize this risk by limiting it to pictures alone, not to text. This will often show you how bad idea it is to specify specific named fonts or their sizes.
Tables are for tabular data.
Not for layout. Doing so means that nothing can be viewed until the whole page is downloaded, which unfairly discriminates against people on modems. Small embedded tables are ok, though. Break any large tables up into manageable chunks. Test viewing of all pages over a 9600 or at most a 19,200 modem connection.