if (document.images)
{
  pic1= new Image(); 
  pic1.src="images/top_menu1_over.jpg"; 

  pic2= new Image(); 
  pic2.src="images/top_menu2_over.jpg"; 
  
  pic3= new Image(); 
  pic3.src="images/top_menu3_over.jpg";
  
  pic4= new Image(); 
  pic4.src="images/top_menu4_over.jpg";
  
  pic5= new Image(); 
  pic5.src="images/top_menu5_over.jpg";
  
  pic6= new Image(); 
  pic6.src="images/top_menu6_over.jpg";
}