if (document.images) {
    img01on = new Image();   img01on.src = "images/btn_home_home_on.gif";
   img02on = new Image();   img02on.src = "images/btn_home_bangalay_on.gif";
   img03on = new Image();   img03on.src = "images/btn_home_fernhill_on.gif";
   img04on = new Image();   img04on.src = "images/btn_home_summit_on.gif";
   img05on = new Image();   img05on.src = "images/btn_home_port_on.gif"; 
   img06on = new Image();   img06on.src = "images/btn_contact_on.gif"; 
   img07on = new Image();   img07on.src = "images/btn_back_on.gif";  
      
   img01off = new Image();   img01off.src = "images/btn_home_home.gif";
   img02off = new Image();   img02off.src = "images/btn_home_bangalay.gif";
   img03off = new Image();   img03off.src = "images/btn_home_fernhill.gif";
   img04off = new Image();   img04off.src = "images/btn_home_summit.gif";
   img05off = new Image();   img05off.src = "images/btn_home_port.gif";
   img06off = new Image();   img06off.src = "images/btn_contact.gif"; 
   img07off = new Image();   img07off.src = "images/btn_back.gif"; 
}

function imgOn(imgName)
{
   if (document.images) {
      document[imgName].src = eval(imgName + "on.src");
   }
}

function imgOff(imgName)
{
   if (document.images) {
      document[imgName].src = eval(imgName + "off.src");
   }
}