Pixel Perfect 
Make your web development Pixel Perfect.
- Home Page: https://github.com/firebug/pixel-perfect/wiki
- Developer Guide: https://github.com/firebug/pixel-perfect/wiki/Developer-Guide
Pixel Perfect is Firefox extension built on top of native developer tools in Firefox.
License
PixelPerfect is free and open source software distributed under the BSD License.
Hacking on Pixel Perfect 2
See Pixel Perfect Developer Guide
Further Resources
- Add-on SDK: https://developer.mozilla.org/en-US/Add-ons/SDK
- DevTools API: https://developer.mozilla.org/en-US/docs/Tools/DevToolsAPI
- Coding Style: https://github.com/mozilla/addon-sdk/wiki/Coding-style-guide
- DevTools Extension Examples: https://github.com/mozilla/addon-sdk/tree/devtools/examples
- DevTools/Hacking: https://wiki.mozilla.org/DevTools/Hacking
- Firefox Developer Edition: https://developer.mozilla.org/en-US/Firefox/Developer_Edition
- Firebug.next wiki: https://getfirebug.com/wiki/index.php/Firebug.next