NS4 = (document.layers);
   IE4 = (document.all);
  ver4 = (NS4 || IE4);   
 isMac = (navigator.appVersion.indexOf("Mac") != -1);
isMenu = (NS4 || (IE4 && !isMac));

if (isMenu){
	
	home_off=new Image(134,20);
	home_on=new Image(134,20);
	comp_off=new Image(134,20);
	comp_on=new Image(134,20);
	prod_off=new Image(134,20);
	prod_on=new Image(134,20);
	deli_off=new Image(134,20);
	deli_on=new Image(134,20);
	garage_off=new Image(134,20);
	garage_on=new Image(134,20);
	late_off=new Image(134,20);
	late_on=new Image(134,20);
	staf_off=new Image(134,20);
	staf_on=new Image(134,20);
	cont_off=new Image(134,20);
	cont_on=new Image(134,20);
	
	home_off.src="images/home-button.gif";
	home_on.src="images/home-button-on.gif";
	comp_off.src="images/company-button.gif";
	comp_on.src="images/company-button-on.gif";
	prod_off.src="images/product-range-button.gif";
	prod_on.src="images/product-range-button-on.gif";
	deli_off.src="images/delivery-net-button.gif";
	deli_on.src="images/delivery-net-button-on.gif";
	garage_off.src="images/garage-customers-button.gif";
	garage_on.src="images/garage-customers-button-on.gif";
	late_off.src="images/latest-news-button.gif";
	late_on.src="images/latest-news-button-on.gif";
	staf_off.src="images/thought-for-the-month-button.gif";
	staf_on.src="images/thought-for-the-month-button-on.gif";
	cont_off.src="images/contact-button.gif";
	cont_on.src="images/contact-button-on.gif";

  }

  function doBtn(imgID,imgName){
    if (isMenu){
      document.images[imgID].src = eval(imgName + ".src")
  }}