One of the best features in the browser is Firefox Sync, which will not only synchronize Firefox across multiple computers, but it will also sync to your Android version of Firefox 4.
Firefox has a deep backbench of add-ons to provide features not found in the standard version of the browser, and you can also customize the interface in ways that you can't with other browsers. Here's how to make your Firefox 4 look like Firefox 3, in case you really miss the old design. It's also a good hands-on tutorial for add-on use, in case you're new to Firefox add-ons.
In the following How To video, we show you how to make Firefox load tabs a bit faster than it does out of the box. This is a great tweak for users who have 20 or 30 tabs open.
App Tabs are a new feature in Firefox to keep your most-used tabs in the same position every time you load the browser. Here's how they work.
Another useful new feature in Firefox 4 is Tab Groups, also known as Panorama. This allows you to keep your tabs accessible but out of sight until you want them. It's excellent for organizing tabs between different interests, and you can label the groups as well.