Why Do You Want to Install Firefox 3.5 on Debian Lenny 5?
One Word: Plug-ins. (Are those two words or is that just one word???)
1. Download Firefox 3.5 for Debian: -or-
$ wget http://www.mozilla.com/products/download.html?product=firefox-3.5&os=linux&lang=en-US
2. Change Directory to /usr/local. That's where we're going to put it:
$ cd /usr/local
3. Untar/Decompress the Firefox 3.5 bzip2 file you just downloaded:
$ sudo tar -xvjf /directory/where/you/put/the/file/firefox*
* Note, it would be best to make use of TAB COMPLETION on the terminal to make sure that you specify the correct file rather than the asterisk.
4. Make a symbolic link
$ sudo ln -s /usr/local/firefox/firefox /usr/local/bin/firefox3
* Note, you can change 'firefox3'to something more convenient like 'ff3'. Either way it works.
* FINAL NOTES: If you get a "No Display Specified" Error or any "Display" related error - simply reboot.