Browser Size is a utility by Google Labs which overlays a semi-transparent image with percentages indicating what part of the website people can see without scrolling. I don’t know how long it has been around, but I found out about it, played a couple of minutes with it, and read the about page a couple of days ago. I mentally stumbled when I read the following.
Browser Size works best on web pages with a fixed layout aligned to the left (emphasis added). If the content reflows as the width is adjusted or it is centered, then the results can be misleading. In this case, you can obtain more accurate results by reducing the browser width to a percentage column, e.g. 90% and seeing what content falls below the 90% horizontal line.
I realize it would be hard to implement it any other way, and I would certainly hope that most people understand you have to play around with the size of your window to use the tool in a meaningful way without having read the preceding message — those that don’t probably won’t read the message either. It seems to me that this should certainly be the preferred way to use the tool — how it works best. Don’t encourage those who produce such annoying designs by saying their methods work best. What they hopefully meant to say is that it works best to expose web pages with a fixed layout for the excrements they are.