Howdy egorgry
If you want all your internet aps (browser, mail, ftp-progs) under one parent-folder I'd recommend you install firefox like this ..
1: Create destination folder ...
by opening a console and entering this command ...
| user@box: mkdir -p /usr/local/internet/firefox |
the "-p"-switch will create all necessary directories too, in case those ain't present. In our case not only the folder "firefox" would be created but also the folder "internet" in case there isn't such a folder already.
2: Install firefox ...
by following the steps of the GUI-installer and specifying /usr/local/internet/firefox as target-directory.
3: Create symbolic links to the firefox-aplication...
Once more we're gonna do this in the console: Enter the command ...
| user@box: ln -s /usr/local/internet/firefox/firefox /usr/bin/firefox |
to create a symbolic link to firefox in /usr/bin. This folder should always be in the path, so this oughta make finding the firefox-executable much easier. A simple "firefox" in a console will then launch the browser.
Alternatively you can also create a desktop-shortcut to /usr/bin/firefox to have the browser available via mouse click, or enter the realm of menu-editing and place a shortcut therein.
hope that helps