A simple yet really useful add-on created by Carlo Casta. Facebook PhotoZoom is a simple extension that integrates directly into Facebook. Just hover over an image — like a profile picture or a photo in an album — and Facebook PhotoZoom enlarges it for you, no need for clicking on the picture and stray away from the page.
A few simple steps to install Facebook PhotoZoom.
1- Click on your Add-on tab on your Mozilla Firefox.
2- Search for Facebook PhotoZoom and click install.
3- Finished the installation and restart your Firefox. Now your PhotoZoom is ready to be use. Just mouse over your cursor to any picture, PhotoZoom will automatically do its job.