If you are using a known javascript library, then you probably will not meet this situation. For instance, you may have a moving code for an image or a div according to the mouse position on screen:
[code='js']
function onMouseMove(e) {
[/code]

Before to any variables, paste this code to make it to work and on IE browsers:
[code='js']
if (e == null)
e = window.event;
[/code]

Otherwise, your javascript code will be stoped by IE.

Even isn’t a big deal at first sight, following a recent list with javascript animantions, i saw that many was not working on Internet Explorer. We like or not, over 35% from internet users (over 45% according to other statistics) use IE browsers – 10% are just for IE6!?!