function errorMessage(source) {
  alert ("Achtung!\n\nBitte überprüfen Sie Ihr"+source +"!");
}

function checkRequiredFields(input) {
	var requiredFields	= new Array("name","telefon","theme");
	var showField			= new Array("en Namen","e Telefonnummer"," Thema");
	var fieldNames			= new Array("name","telefon","theme");
	var fieldCheck			= true;
	for(var fieldNum=0; fieldNum < requiredFields.length; fieldNum++) {
		if ((input.elements[requiredFields[fieldNum]].value == "") || (input.elements[requiredFields[fieldNum]].value == " ")) {
			errorMessage(showField[fieldNum]);
			fieldCheck = false;
		}
	}
	if (fieldCheck == true) {return true;}
		else {return false;}
}