if (document.images) {
  //menu
  var homeOFF = new Image(); homeOFF.src="images/btns/home.gif";
  var homeON = new Image(); homeON.src="images/btns/home_roll.gif";

  var aboutOFF = new Image(); aboutOFF.src="images/btns/about.gif";
  var aboutON = new Image(); aboutON.src="images/btns/about_roll.gif";

  var productsOFF = new Image(); productsOFF.src="images/btns/products.gif";
  var productsON = new Image(); productsON.src="images/btns/products_roll.gif";

  var contactOFF = new Image(); contactOFF.src="images/btns/contact.gif";
  var contactON = new Image(); contactON.src="images/btns/contact_roll.gif";
}

function act(imgName) {
 if (document.images) 
  document[imgName].src = eval(imgName + 'ON.src')
}

function inact(imgName) {
 if (document.images)
  document[imgName].src = eval(imgName + 'OFF.src')
}