function popup(theURL) {
   
      var winWidth = 660;
      var winHeight =500;
      var winLeft = Math.round((screen.width - winWidth) / 2);
      var winTop= Math.round((screen.height - winHeight) / 2);
      window.open(theURL, 'Zoom', 'width=' + winWidth + ',height=' + winHeight + ',left=' + winLeft + ',top=' + winTop);
}

function pruefen()
	{

	var email=(document.kontakt.email.value);
	var re_email=/^([_a-zA-Z0-9-]+)(\.[_a-zA-Z0-9-]+)*@([a-zA-Z0-9-]+\.)+([a-zA-Z]{2,4})$/;
	
   if (document.kontakt.name.value=="" && document.kontakt.email.value=="")
		{alert("Wie können wir Sie erreichen?");
		document.kontakt.name.focus();
		return false;
		}
  
 	if (re_email.test(email)== false)
   	   	{ alert("Keine gültige E-Mail-Adresse!");
     	document.kontakt.email.focus();
    	return false;
    		}
	}