It's probably something simple but, Arggg ... Help please
 

OK, so i have been trying my hand at customizing my forums and I've run into a slight, albeit intensely frustrating problem, (one I'm sure and hoping, many of you would be able to fix in a second). I'm relatively new to all this coding stuff and i don't know how to align everything properly. There seems to be a major discrepancy in the alignment of my forums on different computers. On my computer its perfect, yet on 2 of my family members computers it all haywire. (to wide)
Can anyone help me please :o

here is a link to my forums; www.nannysociety.com/forums


I've se the main table width as 100%