Need to know more statistics about the webpage you are viewing? Check out the extension Tab Data (+Memory usage). It provides the user with tab related stats and memory usage.
Tag Archives | measure
Need to do a little on screen measuring? If you have Firefox then the MeasureIt extension should do the trick.
As you can see it delivers a brain dead simple way of seeing how big that area of your screen is. I could see this tool being really helpful for web developers or anybody else that works with graphics on the Internet.