function checkMail() {
	var x = document.myform.email.value;
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
	if(document.myform.email.value == "") {
		return true;
	}
	if(!filter.test(x)) {
		alert('Email format is not valid!');
		document.myform.email.focus();
		document.myform.email.select();
		return false;
	}
	return true;
}