Getting website to look the same across all monitors

[drumdogg]

After designing my website i found that on different monitors it looks different, with elements being in the wrong place or not centered etc. Even when setting the resolution the same on each monitor it looks different. For example it was designed using a 19'' and recently viewed it on a 17'' and a 24'' and the elements were all over the place.

I have read about using % instead of px in my css. What would be the best approach??

Thanks

 

[drumdogg]

Its different machine and different monitors. Its IE8 that im running and both machines have the same version and same updates.

 

[drumdogg]

Yea same version of windows, XP. It can be big changes too, like a table sitting in the bottom left of the page instead on sitting in the center!