function validate( f ) {
	var msg = '';
	if( f.email.value.length == 0 || !f.email.value.isEmail() ) {
		msg += "your email address\n";
	}
	if( f.phone.value.length > 0 && f.phone.value.length < 10 ) {
		msg += "your phone number must be at least 10 digits including area code\n";
	}
	if( f.message.value.length == 0 ) {
		msg += "your message.";
	}
	if( msg.length > 0 ) {
		alert( "Please fill in the following information:\n\n"+msg );
	}
	return ( msg.length == 0 );
}