Web Newbie - photo issues in Firefox

[BeesKnees]

We're setting up a village domain, and being total newbies have encountered some issues. The main one is that photos are showing fine in IE, but in Firefox many show coarse grey shading - see below

Any suggestions?

 

[BeesKnees]

I'm not sure why IE shows it without the dithering, has it cached an older version of the image which was a jpg?

No, there can't be any cached versions as the site only went live today. Maybe it's because the pages were created in MS Publisher, and are therefore more compatible with IE? Our domain host told us we should use Adobe Dreamweaver ... but not on our budget!