Good question.
Yes it is possible with the following code added to your page (either in the head section of at the end of your page):
<script type="text/javascript">
function eventFire(el, etype) {
if (el.fireEvent) {
(el.fireEvent('on' + etype));
} else {
var evObj = document.createEvent('Events');
evObj.initEvent(etype, true, false);
el.dispatchEvent(evObj);
}
}
function openTheFirstMenuItem() {
var item1 = document.getElementById("ddmenu");
if (item1 && ddmenu) {
item1 = item1.getElementsByTagName("li")[0];
eventFire(item1, "mouseover");
}
else setTimeout(arguments.callee, 50);
}
openTheFirstMenuItem();
</script>