window.event.keyCodeとevent.which

      Netscape/Firefox/Opera     window.event.keyCode,   event.which  
  IE event.keCode               ， NetScape/FireFox/Opera    event.which


      onkeydown  
onkeydown="javascript:if((window.event?window.event.keyCode:event.which)==13 && longinTest()) form1.submit();"

<script language="javascript">
function longinTest() {
	var name = document.form1.userName.value;
	var pass= document.form1.passWord.value;
	if (name == "" || pass== "") {
		if (name == "" && pass== "") {
			alert("         !");
			document.form1.userName.focus();
		} else if (name == "" && pass!= "") {
			alert("      !");
			document.form1.userName.focus();
		} else if (name != "" && pass== "") {
			alert("     !");
			document.form1.passWord.focus();
		}
		return false;
	} else {
		return true;
	}
}
</script>