if (document.images) {  // If the image object exists    
      // Preload images
        off = new Array(6)
        on = new Array(6)
        screenon = new Array(6)
    on[1] = new Image();          
    on[1].src = "/images/btn_demoreel_on.gif";       
    on[2] = new Image(); 
    on[2].src = "/images/btn_gallery_on.gif";   
    on[3] = new Image();          
    on[3].src = "/images/btn_about_on.gif";       
    on[4] = new Image();          
    on[4].src = "/images/btn_blog_on.gif";
    on[5] = new Image();          
    on[5].src = "/images/btn_contact_on.gif";                      
    on[6] = new Image();          
    on[6].src = "/images/btn_home_on.gif";                      

    off[1] = new Image();         
    off[1].src = "/images/btn_demoreel.gif";     
    off[2] = new Image(); 
    off[2].src = "/images/btn_gallery.gif";
    off[3] = new Image();         
    off[3].src = "/images/btn_about.gif";     
    off[4] = new Image();         
    off[4].src = "/images/btn_blog.gif";
    off[5] = new Image();         
    off[5].src = "/images/btn_contact.gif";   
    off[6] = new Image();         
    off[6].src = "/images/btn_home.gif";   
    } 

    function buttonOn(buttonName,num) {  
        if (document.images) { // If the image object exists   
          // Change images on the page
          document[buttonName].src = on[num].src;
        }
    }

    function buttonOff(buttonName,num) {  
        if (document.images) { // If the image object exists   
          // Change images on the page
          document[buttonName].src = off[num].src;
        }
    }