Move the mouse over the field below.

When looking at the code, note that there is no space between tags so the images mortize (i.e. move together without any space between).

It seems that the events onMouseOver and onMouseOut are not implemented as events which can be used with images. This is why we have to make the images clickable images (using the anchor tag), and then use the eventhandlers of the anchor. To do this make sure you'll set onClick to "return false;", so the click event is stopped there and HTML does not try to follow the (nonexistent link) in the href tag.