Firefox 4, the Fox shows who’s the king.

Today, March 22th, Mozilla have launched Firefox 4.
The new browser, supporting naturally HTML 5, is a lot
faster than it’s predecessor, as well as holding a new design,

similar to the Chrome design, but still maintaining the Firefox look.

Extensions
Many extensions are not yet supported,  this is
normally a matter of the developers of those extensions, to
update them and make them work on the new version.

Although when Firebug is working - all the rest can wait.
(actually TwitterBar, Greasemonkey and Adblock are working too)

the Add-ons Manager opens now on a tab, neat, looks like Chrome.

HTML 5
As far as I’ve seen, Parsing, Canvas (really important for some of my projects!),
Video

with the exception of Subtitle and the sacred H.264 [wtf]
Mozilla chose the WebM support instead, Google seems to be
going in that direction as well, that’s mainly because H.264 is
not an Open Codec.

Audio

Ogg and WebM support, intentionally living AAC and MP3
out of the game, it seems that Mozilla is planning to force the web
to be as Open as possible (hear, hear!)

Other than that, there’s a very partial form element support
(shouldn’t worry anyone, since I personally don’t see the idea of these
new form elements anyway).
Drag & Drop, Session History, and Application Cache
and Session Storage are supported!
(this should reduce the average JS file by 80%)

Web Workers support, allowing Threading of actions

Naturally, some of those things were supported in previous versions of Firefox.

The Small Things

You can now make Tab groups, which I don't really understand why, but ok
as well as Tab App (which means that you can have your gmail always open for instance).
I liked the fact that if I type in an address and the tab is already open - it switches to it.

How To Install on Ubuntu?
I simply extracted the tar.gz file, copied it into my /opt/ folder
(you can copy it to your /home/ as well), and changed the symbolic link

sudo ln -s /opt/firefox/firefox /usr/bin/firefox

This way it replaces the current Firefox, you can also backup the old
Firefox link if you wish.

Surf's Up!