my first experience with plug-ins on firefox and i am blown away. This is a set of tools that help highlight on a web page various web design elements.
I was initially dubious because the screen shots were on windows, but i clicked the download link anyway. I was pleasantly surprised by a dialog box asking me if I wanted to install the selected extension, well sure. Here’s a screen shot of the tool in action, note the bookmark bar, those are all the tools, kudos, kudos, kudos, great job: