function changeImages() {
 if (document.images && (preloadFlag == true)) {
  for (var i=0; i<changeImages.arguments.length; i+=2) {
   document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
  }
 }
}
var preloadFlag = false;
function preloadImages() {
 if (document.images) {
  preloadFlag = true;
 }
}

function swapTo(section){
 changeImages(section,'/images/'+section+'_on.gif');
 }
 
function swapBack(section){
 changeImages(section,'/images/'+section+'_off.gif');
 }