This is my favorite new tool from Google which just came out early Dec. 2009. – BROWSER SIZE – This page allows you to see which parts of your site are able to be seen by the smallest of browsers. I personally always design no WIDER than 1000px with a possible stretchy width beyond that. But this is a neat tool because it gives you insights into the DEPTH and where your headline goes or your call to action on the page. I just redesigned my whole header of my site after realizing things were too low.