function validate() {

	var reg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/;
	var address_1 = document.forms['mailform'].elements['email'].value;

	if(reg.test(address_1) == false) {
		alert('Bitte geben Sie Ihre korrekte E-Mail-Adresse an / Please be kind to provide a valid E-mail address');
		document.forms['mailform'].elements['email'].focus();
		document.forms['mailform'].elements['email'].value = "";
		return false;
	}

}