post the script part of the header, and the some of the map script, so we can see what you did wrong.
Did you load the draw map in the body tag, onload event?
The page, or DOM has to be ready, and the draw map has to load, in order for the map to display. So either the DOM is not ready, or your not loading the function.
It's 11pm here, i'm out to sleep.
<script>
function initialize() {
}
</script>
<body onload="initialize()">
<div id="map_canvas"></div>
</body>