if (document.images)
{
  pic1= new Image(64,39); 
  pic1.src="images/nav/home_over.gif"; 
  
  pic2= new Image(84,39); 
  pic2.src="images/nav/about_over.gif"; 
  
  pic3= new Image(156,39); 
  pic3.src="images/nav/products_services_over.gif"; 
  
  pic4= new Image(96,39); 
  pic4.src="images/nav/contact_over.gif";
}