Testing your web sites at lower resolution is always a good idea (no the rest of the world doesn't view web sites at 1680x1050 like web developers sometimes do). Here's a quick tip that will let you resize your browser window to a specific size.

According to some stats released by OneStat only 18.23% of browsers are using 800x600 these days, down from 24.66% last year.

A whopping 57.38% use 1024x768, the rest use something higer (I'm sure there are still a few 640x480's out there viewing the web with CGA graphics card).