prova così:

codice:
<script language="JavaScript">
<!--
function goto(){
	if (document.list.ch.options[document.list.ch.selectedIndex].value != "all") {
		window.location.href = "tutorials.php?a=l&c="+document.list.ch.options[document.list.ch.selectedIndex].value;
	}
}
//-->
</script>
ciao