How to reinstall Firefox

sudo apt-get --reinstall install firefox

If you want default settings then simply run:

mv ~/.mozilla ~/.mozilla_old

Then rerun the browser and you will get the default settings (This will also remove Thunderbird settings but we can rename those back if this is te case)

Actionparsnip PLEASE help me with this one, I don’t have web connection since the 9th of February and badly need it.
On the 24th of February I add more information to question 16425 but dint received a answer, so I decide to reinstall Firefox but unsuccessful, result follows:

luis@luis-desktop:~$ sudo apt-get --reinstall install firefox
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
qt3-assistant libbabl-0.0-0 linux-headers-2.6.32-21 libgegl-0.0-0 ruby1.8
ruby linux-headers-2.6.32-21-generic qt3-doc libgimp2.0 libruby1.8 gimp-data
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 61 not upgraded.
Need to get 11.4MB of archives.
After this operation, 0B of additional disk space will be used.
Do you want to continue [Y/n]? y
Err http://za.archive.ubuntu.com/ubuntu/ lucid-updates/main firefox 3.6.13+build3+nobinonly-0ubuntu0.10.04.1
Could not resolve 'za.archive.ubuntu.com'
Err http://security.ubuntu.com/ubuntu/ lucid-security/main firefox 3.6.13+build3+nobinonly-0ubuntu0.10.04.1
Could not resolve 'security.ubuntu.com'
Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/f/firefox/firefox_3.6.13+build3+nobinonly-0ubuntu0.10.04.1_i386.deb Could not resolve 'security.ubuntu.com'
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
luis@luis-desktop:~$

Thanks actionparsnip, that solved my question.