Andrew,
You seem to be forgetting the 'idiot' part of 'idiot proof instructions'.

: tuart: No such file or directory
[root@localhost ~]# su - stuart
[stuart@localhost ~]$ cd /home/stuart/desktop/
-bash: cd: /home/stuart/desktop/: No such file or directory
[stuart@localhost ~]$ su -
Password:
[root@localhost ~]# cd /home/stuart/desktop/firefox-1.5.0.2.tar.gz
-bash: cd: /home/stuart/desktop/firefox-1.5.0.2.tar.gz: No such file or directory
[root@localhost ~]# cd /home/stuart/desktop/
-bash: cd: /home/stuart/desktop/: No such file or directory
[root@localhost ~]# cd /home/stuart/Desktop/
[root@localhost Desktop]# ./configure
-bash: ./configure: No such file or directory
[root@localhost Desktop]# tar zxf firefox-1.5.0.2.tar.gz
[root@localhost Desktop]# ./configure && make && make install
-bash: ./configure: No such file or directory
[root@localhost Desktop]# tar zxf firefox-1.5.0.2.tar.gz./configure && make && make install
tar: firefox-1.5.0.2.tar.gz./configure: Cannot open: No such file or directory
tar: Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error exit delayed from previous errors
[root@localhost Desktop]#