Just wasted an hour debugging a simple site because of this.
When writing inline javascript for IE, don't use the standard
application/javascript-type because Internet Explorer won't run the code.
<!-- Doesn't work with IE -->
<script type="application/javascript">
var testing = 1;
</script>
Just change the MIME-type to text/javascript and you're good to go:
<!-- Works in all browsers -->
<script type="text/javascript">
var testing = 1;
</script>