if (document.images)
{
  pic1= new Image(); 
  pic1.src="images/scroll_left_open.gif"; 

  pic2= new Image(); 
  pic2.src="images/scroll_left.gif"; 

  pic3= new Image(); 
  pic3.src="images/scroll_right_open.gif"; 

  pic4= new Image(); 
  pic4.src="images/scroll_right.gif";

}