[CentOS] remote ssh to machine how display firefox

> I can ssh into a remote machine.
> I can start X on that machine with startx

No need to start X on the remote machine.  You need to do "ssh -X  
<remotemachine>" so that X is forwarded (back to the machine that you  
ssh'ed from).  Make sure that "X11Forwarding yes" is set in the /etc/ 
ssh/sshd_config file (restart the sshd if it was not).  Then you can  
simply type "firefox &" and it will appear on the machine you started  
the ssh from (assuming of course that a X server is running  
locally).  This of course works for any X11 application, not just  
Firefox.

Alfred