var timerID = null; 
var timerOn = false; 
var timecount = 1500;
 
function hideAll () {
 document.getElementById('rb1').style.display='none';
}
function showDiv (divname) {
 hideAll();
 document.getElementById(divname).style.display='block';
}

function startTime() { 
 if (timerOn == false) { 
 timerID=setTimeout( "hideAll()" , timecount); 
 timerOn = true; 
 } 
}
function stopTime() { 
 if (timerOn) { 
 clearTimeout(timerID); 
 timerID = null; 
 timerOn = false; 
 } 
}