X11 sleep mode?

[Laurence Sanford]

When I leave my web browser (Firefox) open on my desktop looking at a 
page that should refresh every couple of minutes until a process 
completes, things will simply quit updating after some time passes. 
Sometimes it's only a few minutes, sometimes its several hours, but when 
I come back to the computer, it immediately tries to pick back up. This 
hasn't been a problem yet, but it is foreseeable as a problem in the 
future. Is there a way to keep whatever is "sleeping", be it X or 
Firefox, from doing so?

FreeBSD colossus.cotharyus.net 5.4-STABLE FreeBSD 5.4-STABLE #7: Wed 
Jun  1 16:32:23 CDT 2005     
lauasanf at colossus.cotharyus.net:/usr/obj/usr/src/sys/Colossus  i386

Running X11 v4, enlightenment wm