Make your CSS looks exactly to your design with a image comparasion
Pixel Perfect allow you to compare in real time your design in JPG / PNG with your current integration to fix your CSS.
The must have extensions for web integration and front-end developper
Pixel perfect is an extension for Chrome (maybe firefox in the future)
This extension open a window with a dropzone, then you drag and drop your design and go for Preview
It will open a slider on the current tab to compare the design or mockup to the actual integration