<script type="text/javascript">
function resizeWindow() {
	var tableWidth, full;
	tableWidth = document.getElementById('mytable').offsetWidth;
	full = document.getElementById('full').offsetWidth;

	if (tableWidth > full) {
			alert("to much");
	} else {
		alert("your good");
	}
}

window.onresize = resizeWindow();
</script>