Imagemaps are a bit old hat these days, but they still have their uses and this IE bug can be a real killer.

If you dynamically create an Imagemap using Javascript, IE has a problem with polygon areas that have different number of co-ordinates. Basically, IE will crash if you click on an area that has fewer co-ordinates than a previous area.

To get around this, don’t use DOM element properties to create your Imagemap:

Don’t use:

map_image.isMap = ‘ismap’;
map_image.useMap = ‘#layer0′;

etc

Put your IMG tag inside a SPAN instead, and update it using the innerHTML property.

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.