At how much distance, should we place monitor?

i think a read in some mag that there was a formula for that which involved the screen size in inches but it was for CRT monitors, i dont have a clue about lcds and plasmas

i think it is about four fit from your sitting chair................

I would like to add here that there are two types of monitors, one is that traditional one having cathod ray tube and other is LCD. The first one is much harmful for the eye sight. But you can place a filter glass between the direct rays to your eyes. There is generally 2 and half feet distance to a 15 inch monitor, ammm I guess so. Why you don't go for LCD? ;)