Never had to worry about this before because usually I use a fixed size set for 800x600 and everyone else with much bigger resolutions can lump it

So as I am preparing to convert all my tables sites to css I am going to use the holy grail type 3 column layout and use %'s so that all my visitors get the best use of their screen size.

Of course I want to ensure that it looks acceptable at any size, minimum being 800x600.

My question then is how can I see the site as I build it at different resolutions? I dont want to keep changing my own screen resolution every time I want a quick look to ceheck it at 800x600 or 1024x768.

Any ideas?