if (document.images) {
        
  b1off = new Image;  b1off.src = "images/home.gif";
  b1on  = new Image;  b1on.src  = "images/homeon.gif";
  b2off = new Image;  b2off.src = "images/loadingramps.gif";
  b2on  = new Image;  b2on.src  = "images/loadingrampson.gif";
  b3off = new Image;  b3off.src = "images/augerdrives.gif";
  b3on  = new Image;  b3on.src  = "images/augerdriveson.gif";
  b4off = new Image;  b4off.src = "images/skidsteer.gif";
  b4on  = new Image;  b4on.src  = "images/skidsteeron.gif";
  b5off = new Image;  b5off.src = "images/levelbar.gif";
  b5on  = new Image;  b5on.src  = "images/levelbaron.gif";
  b6off = new Image;  b6off.src = "images/aluminiumtrailers.gif";
  b6on  = new Image;  b6on.src  = "images/aluminiumtrailerson.gif";
  b7off = new Image;  b7off.src = "images/liteguard.gif";
  b7on  = new Image;  b7on.src  = "images/liteguardon.gif";
  b8off = new Image;  b8off.src = "images/pitforming.gif";
  b8on  = new Image;  b8on.src  = "images/pitformingon.gif";
  b9off = new Image;  b9off.src = "images/enquiryform.gif";
  b9on  = new Image;  b9on.src  = "images/enquiryformon.gif";
  b10off = new Image;  b10off.src = "images/contact.gif";
  b10on  = new Image;  b10on.src  = "images/contacton.gif"

}

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

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