//walks trough all the elements of the page, 
	//and empties all visible elements.
	function emptyVisibleFields() {
		emptyAllInputFields();
		emptyAllLabels();
	}
	
	
	//empties all visible textinputfields
	function emptyAllInputFields() {
		var inputFieldList = document.getElementsByTagName("input");
      	for (var i = 0; i < inputFieldList.length; i++) {
       		var element = inputFieldList[i];
       		var visible = element.getAttribute('visible');
       		var defaultValue = element.getAttribute('defaultValue');
    		if (element.type == "text" && visible == "true") {
     			//clear its value
     			if (defaultValue != null){
     				element.value = defaultValue;
     			} else {
    				element.value = "0";
    			}
      		}
      	}
	}
	
	
	//empties all visible labels
	function emptyAllLabels() {
		var labelList = document.getElementsByTagName("label");
      	for (var i = 0; i < labelList.length; i++) {
       		var element = labelList[i];
       		var calculatoroutput = element.getAttribute('calculatoroutput');
       		var visible = element.getAttribute('visible');
    		if ( visible == "true" && calculatoroutput != "" && calculatoroutput != null) {
     			//clear its value
    			element.innerHTML = "0";
      		}
      	}
	}