Google Chrome v.23: New Ruler Feature

With the release of Chrome version 23, you are in for a pleasant surprise! The developer tools (F12) now offer a horizontal and vertical rule built-in to the browser window when inspecting elements.

1. Right click an element on the page and click "Inspect Element"
2. Developer Tools will open at the bottom of your screen
3. Hover over any element in that window and you'll see it highlighted in your browser...
4. and there will be horizontal/vertical rules

Now guessing at positioning and sizing is made much easier. Thanks Google!