function check_contact_form() {
	var msg="";
	if ( IsEmpty(document.contact_form.firstname) ) 	msg += "- Please enter your first name\n";
	if ( IsEmpty(document.contact_form.zip) ) 				msg += "- Please fill out the postal code\n";
	if ( IsEmpty(document.contact_form.email) ) 			msg += "- Please fill out the email\n";
	
	if ( msg.length > 1 )
	{
		alert ( msg );
		return false;
	}
	return true;
}

function IsEmpty(aTextField) {
	if ( (aTextField.value.length==0 ) || (aTextField.value==null) ) 
		return true;
	else
		return false;
}