Help! how do I fix pixelated thumbnails and rollovers?

[jai.villa]

I am having a web designer in Romania build my website, but it seems the thumbnail images and rollover images he's put in place are a bit pixelated. He insists that on his end there are no pixels, but I've tried on several different PCs and monitors, and it shows as slightly pixelated!

Can you think of a reason why this might be happening? I'm stumped.

To make matters more confusing, I used my Mac laptop to have a look, and now the images were fine (not pixelating). But now the rollovers don't work! The images SHOULD be slightly faded until you rollover the image then it lights up.

The site is www.vain.com.au/index1.php

Any suggestions? How can I make sure the best quality image possible?

Help!

[aeroweb99]

They look like they were maybe a little over optimized but they don't look bad, Just to a trained eye maybe.