function isUser(vuser){
	var lists = "1234567890abcdefghijklmnoqprstuvwxyzABCDEFGHIJKLMNOQPRSTUVWXYZ";
	var match = true;
	var found = false;
	var chars = "";
	for (var i = 0; i < vuser.length; i++) {
		chars = vuser.charAt(i);
		found = false;
		for (var j = 0; j < lists.length; j++) {
			if(lists.charAt(j) == chars) {
				found = true;
				break;
			}
		}
		if (!found) {
			match = false;
			break;
		}
	}
	return match;
}

function chkfrm(vfrm){
	var err = "";
	var vuser = vfrm.elements['user'].value;
	var vpass = vfrm.elements['pass'].value;

	if (!(vuser.length > 2 && isUser(vuser))) err += "- Invalid username\n";
	if (vpass.length < 4) err += "- Invalid password\n";

	if (err != "") {
		alert("Attention:\n\n" + err);
		return false;
	} else return true;
}