I use an image map for the kids side of www.lab6.co.uk

There is a large graphic divided into coloured squares with a gif cartoon cut and pasted on top of the squares. I then create a hotspot html link to that web page.

When I cut and paste the cartoons (transpaent background gifs) the colours become mottled / spotted instead of a smooth fill with one colour. Why?

This really messes up the big image as you can see on the squares already used. How do I cut and paste perfectly with PSP?