How Google Browser Size Works
Important message: we've graduated from Google Labs! Please use the In-Page Analytics report within Google Analytics to view accurate analyses of traffic to your site.
This tool will shut down early July 2012. See the announcement for more details.
Google Browser Size is a visualization of browser window sizes for people who visit Google. For example, the "90%" contour means that 90% of people visiting Google have their browser window open to at least this size or larger.
This is useful for ensuring that important parts of a page's user interface are visible by a wide audience. On the example page that you see when you first visit this site, there is a "donate now" button which falls within the 80% contour, meaning that 20% of users cannot see this button when they first visit the page. 20% is a significant number; knowing this fact would encourage the designer to move the button much higher in the page so it can be seen without scrolling.
To view your own Web site with this same visualization overlaid on it, simply type its URL into the "Enter URL here" textbox at the top of the window and click Go.
The Google Browser Size team