function displayPageImage()
{
  var imgO = document.getElementById("page_img");
  imgO.src = PAGE_IMAGE;
}

function fillMenu(mnuId)
{
  var mnuO = document.getElementById(mnuId);
  mnuO.className = "main_menu_fill";
}
function clearMenu(mnuId)
{
  var mnuO = document.getElementById(mnuId);
  mnuO.className = "main_menu_clear";
}

<!-- Begin
// Set up the image files to be used.
var theImages = new Array() // do not change this
// To add more image files, continue with the
// pattern below, adding to the array.

theImages[0] = 'images/headers/Bridge_Light_Bulb.jpg'
theImages[1] = 'images/headers/Grass_Thermo.jpg'
theImages[2] = 'images/headers/insulators.jpg'
theImages[3] = 'images/headers/River_Energy_Star.jpg'
theImages[4] = 'images/headers/sky_fan.jpg'
theImages[5] = 'images/headers/Soccer_Switch.jpg'

// do not edit anything below this line

var j = 0
var p = theImages.length;
var preBuffer = new Array()
for (i = 0; i < p; i++){
   preBuffer[i] = new Image()
   preBuffer[i].src = theImages[i]
}
var whichImage = Math.round(Math.random()*(p-1));
function showImage(){
  //document.write('<img src="'+theImages[whichImage]+'">');
  var picObj = document.getElementById('page_picture_box');
  picObj.background = theImages[whichImage];
  picObj.style.backgroundImage = theImages[whichImage];
  // the line below causes javascript error in Internet Explorer
  //picObj.style.background = theImages[whichImage];
  picObj.background = theImages[whichImage];
  picObj.setAttribute('background', theImages[whichImage]);
}




//  End -->