Here is some curious Firefox behaviour I’ve recently discovered. It took me several hours to figure out what was happening.
If you place an imagemap inside a DIV in Firefox, it works fine.
However, if you then float that DIV, Firefox moves the image with the DIV, but leaves behind the imagemap where the DIV would have been had it not been floated.
IE doesn’t repeat this behaviour. It moves the imagemap with the image. I’m not sure which is the standardised behaviour, but if you want to place imagemaps in columns on a page, and you want this to work in Firefox, you have to use tables. DIVs won’t cut it.