What is the Best Tv Height?

I have a tv that is an LCD 42" LG. I can't decide if I want it on a ledge on the ground or higher up. Is there a site that talks about height? I found viewing distance but I can't seem to find anything on height. What is the best place to put the tv and can anyone tell me sites to read this on?

Suggestion:

I recently wall mounted my LG 42 LF7700 .The wall mount instructions stated the best hight was eye level (hight while seated) so as not to cause neck strain.
http://img819.imageshack.us/img819/5004/mytv.jpg

Tagged as: optimum height of tv from the ground, tv height from ground