if (document.images) 
  { 
    var img = new Object(); 
    img["1"] = new Image(36, 21);  
    img["1"].src = "img/about_a.gif";  

    img["2"] = new Image(48, 21);  
    img["2"].src = "img/contact_a.gif";
  
    img["3"] = new Image(34, 21);  
    img["3"].src = "img/home_a.gif";  

    img["4"] = new Image(45, 21);  
    img["4"].src = "img/portfolio_a.gif";
    
    img["5"] = new Image(36, 21);  
    img["5"].src = "img/about.gif";  

    img["6"] = new Image(48, 21);  
    img["6"].src = "img/contact.gif";
  
    img["7"] = new Image(34, 21);  
    img["7"].src = "img/home.gif";  

    img["8"] = new Image(45, 21);  
    img["8"].src = "img/portfolio.gif";

  }