The definition of simple elegance! Rated 5 out of 5 stars

Smooth and really useful! I use it ALL the time. This add-on reminds me of the kind of utilities I used to write before I abandoned the business world. But it COULD be even better with:

-- Units (numbers) at each 100 pixel hash mark ("100px", "200px", etc...) like a ruler has, and add an option to select the digit font, or at least to make it bold.

-- Configurable fill color and transparency for the rectangle selection. Try using it on a page nearly the same color blue as the fixed fill color.

-- Don't grey out the screen! Instead, use a dlg box saying that you're in measureit, with an "exit measureit" button. If you spend time in another window and and forget, you have a hell of a time figuring out why firefox is "hung". And it was NOT obvious the first time I used it that I had to click the little icon again. This box should be suppressable in config, which should let you choose the dlg box, the grey-out (as it is now), or no indication At least make the icon in the status bar be fluorescent orange or something.

-- make the point at the center of the crosshair bright red

-- Show the area of the selection too (width times height)

-- keep the little numbers box above (or below) the crosshairs all the time. As it is, the box sometimes moves and sometimes doesn't, depending on some inscrutable combination of where on the screen you start the selection, the direction you drag, and how far you drag the crosshair.

-- an option to change the color of the crosshair

-- when you hold down BOTH mouse buttons, magnify the screen near the crosshair. This is necessary for when you need an exact distance, not "almost" the right answer.

-- You can't see the grey crosshair on a grey background (like the bar at the top of blogger) and you can barely see it on many other backgrounds. Instead, make the pixels which are the crosshair be either full white or full black, depending on the luminosity of the background at that point.

-- faye kane homeless brain

This review is for a previous version of the add-on (0.4.5).