var IDLE_TIMEOUT = 270; //seconds 45min

var _idleSecondsCounter = 0;
document.onclick = function() {
  _idleSecondsCounter = 0;
};
document.onmousemove = function() {
  _idleSecondsCounter = 0;
};

document.onkeypress = function() {
  _idleSecondsCounter = 0;
};
window.setInterval(CheckIdleTime, 1000);

function CheckIdleTime() {
  _idleSecondsCounter++;
  var oPanel = document.getElementById("SecondsUntilExpire");
  if (oPanel)
    oPanel.innerHTML = (IDLE_TIMEOUT - _idleSecondsCounter) + "";
  if (_idleSecondsCounter >= IDLE_TIMEOUT) {
    //alert("Your Session Time expired. Please Login.");
    document.location.href = "logoff.php";
  }
}