var imgRolloverPrevOver = new Image() ;
  imgRolloverPrevOver.src = 'prev_over.gif';
var imgRolloverPrevOut = new Image() ;
  imgRolloverPrevOut.src = 'prev_down.gif';

function onRolloverPrevOver() {
  document.RolloverPrev.src=imgRolloverPrevOver.src;
}
function onRolloverPrevOut() {
  document.RolloverPrev.src=imgRolloverPrevOut.src;
}
 
var imgRolloverTopOver = new Image()
  imgRolloverTopOver.src = 'top_over.gif';
var imgRolloverTopOut = new Image()
  imgRolloverTopOut.src = 'top_down.gif';

function onRolloverTopOver() {
  document.RolloverTop.src=imgRolloverTopOver.src;
}
function onRolloverTopOut()  {
  document.RolloverTop.src=imgRolloverTopOut.src;
}
 
var imgRolloverNextOver = new Image()
  imgRolloverNextOver.src = 'next_over.gif';
var imgRolloverNextOut = new Image()
  imgRolloverNextOut.src = 'next_down.gif';

function onRolloverNextOver() {
  document.RolloverNext.src=imgRolloverNextOver.src;
}
function onRolloverNextOut() {
  document.RolloverNext.src=imgRolloverNextOut.src;
}