Firefox 4 to get App Tabs
Firefox 4 is set to get an amazing new tab feature that I think will change the way users think about tabs.
It's called the 'App Tab' and it's currently in the Firefox 4 Beta 2 nightlies (so no, it's not generally available, yet).
The basic idea is that there are many web applications (think Gmail) where you want to not just 'bookmark' the site but have a dedicated tab. With the App Tab, the app (say Gmail) gets its own dedicated tab which stays at the far left of the tab strip, making it easily accessible to users. (click the image above for my test case with Gmail as an App Tab).
I use multiple websites (Gmail, Twitter, Facebook etc) that I revisit multiple times over the course of the day. Having to find those open tabs on my current Firefox 3.6.6 tab strip is sometimes a challenge. With App Tabs, that's no longer the case and it makes for an dramatically improved browser experience.
As this is an under-development feature, it's not fully baked in the nightlies and not yet a publicly available feature for all, but it's one that I personally think will make the next Firefox 4 Beta an interesting experience for testers.