Because IE is like Deathstar, bad for all people.
http://groups.google.com/groups?th=e...1b1eda2&rnum=1
There is a technicality related to form submission if you use an image submit button. It is usually relevant only if you have several such buttons in one form. That's perfectly valid per se, but the usual instructions for including several submit buttons do not apply as such. When using image submit buttons, you need to use specifically different NAME attributes in order to be able to recognize in the form handler which button was clicked on.
The reason to this is the way in which image submit buttons contribute to form data set: the value of the VALUE attribute is ignored, and the coordinates of the clicked location are passed instead. For example, if you have <input type="image" src="submit.gif" name="foo" value="bar">, then the form data set contains the fields foo.x and foo.y, with numeric values that indicate the x and y coordinates of the clicked location.
http://www.cs.tut.fi/~jkorpela/forms/imagebutton.html