function change(cal){ 
  	var url = document.getElementById(cal).src;
//	alert(url);
	if(url.indexOf("off")>=0){
		url = url.replace('off','on');
		document.getElementById(cal).src = url;
	}else{
		url = url.replace('on','off');
		document.getElementById(cal).src = url;
	}
  }// JavaScript Document