Bookmark Page Button
Bookmarks are the heart of the web browser, remembering where the great page your saw the other day can be quite hard, so you bookmark it. Having a convenient button to quicken the process just makes so much sence.
Add-ons Button
This being the most downloaded button I have made speaks for itself. The add-on's window allows the installation and management of all your extensions and themes. If you need an update, change a setting, swap themes or enable/disable an add-on the Add-ons' window is the black to go. Being able to access this quickly is a necisity for many.
Install Button
Installing Extensions and particularly themes that you have downloaded can be quite a trick. This button makes the process simple and hassle free.
Status Bar Button
Toggle the status bar from hidden to shown. Hide it to get the most out of your screen space, and show it when it's really needed.
Options Button
Firefox, Thunderbird and Sunbird all have a huge number of settings. Often you will find a need to change one. About to visit your banking site, so you want pop ups enabled, or what ever your current need might be. The button brings the option window to you quicker.
Bottom Button
Go to the very bottom fo the current page.
Print Preview Button
Paper costs money (and trees) so it is worth checking what the page looks like before you print it. Though it has always amazed me just how much the button gets downloaded.
Restart Button
There is a number of reason you may want to restart the program your using. Though having installed an extension is the most common. This button take all the hassle and work out of it.
Undo Close Tab Button
Reopen the last closed tab. Really nice when a tab is closed by mistake, or you decided you did not really want to close it moments too late.
Gmail Button
Gmail, Google's massively popular web based email. Checking if you have a new email becomes an often repeated task. This button serves as a second "home page" button, bring you to your email quicker and will less hassle.