That's the whole command. 'file' is a command to test for filetype.
Although, doesn't seem much use here: just says 'data'.
I tried the link and get the same results. Here's the checksum:
oscar0:~# md5sum /tmp/firefox-i686-linux-gtk2+xft-1.tar.gz
This archive is broken I believe. It doesn't respond to gzip,bzip, or plain tar.