// Simon Willison's addLoadEvent function to handle registering several window.onloads. 
// http://simon.incutio.com/archive/2004/05/26/addLoadEvent
function addLoadEvent(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      if (oldonload) {
        oldonload();
      }
      func();
    }
  }
}
function addUnLoadEvent(func) {
  var oldonunload = window.onunload;
  if (typeof window.onunload != 'function') {
    window.onunload = func;
  } else {
    window.onunload = function() {
      if (oldonunload) {
        oldonunload();
      }
      func();
    }
  }
}