[ Thanks to Chris7mas for this link.
]
“Debian Lenny comes with Iceweasel 3.0.3, which is
actually Firefox with a changed name and a few minor changes. If
you have Iceweasel 3.0.3 installed but want to test this new beta
without changing anything to your system, just follow the steps
below.Download Firefox 3.1 Beta 1 Get the Firefox .tar.bz2 archive
from here, then uncompress it using:tar -xjf firefox-3.1b1.tar.bz2
Next, move the firefox directory wherever you want it, for
example in your home directory, or in ~/apps etc.”