Update: I guess I missed this, but something very similar to this made it into Chrome…
The other day I read an article mentioning the Boston Globe embracing responsive design. The site was great, but I was having trouble determining screen widths and couldn’t find a tool to easily do this, so I made this for myself. It was easy enough to make so I thought I’d share it with you.
There may be something else that accomplishes the same thing, if there is, sorry, I didn’t see it.
Once the bmklt or extension is clicked, it toggles the rulers over the current page content. The z-index is like 600000 or something, so if someone has a super-high z-index, it may not work. Also, it seems to not work on some Google stuff, but this didn’t really matter too much to me.
It looks like this in use (links below):
Firefox extension: L-Square
This link will take you to the Mozilla Add-Ons site.
Chrome extension: L-Square
This link will take you to the Chrome web store.
Note: You may need to reload your current page after you install the extension.
Disclaimer: This is my first attempt at extensions. Please forgive me if they suck.