function validEmail (s)
{//prüft, ob Emailadresse valide ist
var a = false;
var res = false;

if (typeof(RegExp) == 'function') {

	var b = new RegExp('abc');
	if(b.test('abc') == true){a = true;}
	}

if(a == true) {
  	reg = new RegExp('^([a-zA-Z0-9\\-\\.\\_]+)'+'(\\@)([a-zA-Z0-9\\-\\.]+)'+'(\\.)([a-zA-Z]{2,4})$');
	res = (reg.test(s));
	}
else {
	res = (s.search('@') >= 1 && s.lastIndexOf('.') > s.search('@') && s.lastIndexOf('.') >= s.length-5);
         }

return (res);
}//end function