if (document.images) 
{
   img1 = new Image();
   img2 = new Image();
   img3 = new Image();
   img4 = new Image();
   img5 = new Image();
   img6 = new Image();
   img7 = new Image();
   img8 = new Image();         
   img1.src = "images/subnav_clayProducts_a.gif";
   img2.src = "images/subnav_culturedstone_a.gif"
   img3.src = "images/subnav_face_a.gif";
   img4.src = "images/subnav_glassBlock_a.gif"
   img5.src = "images/subnav_limestone_a.gif";
   img6.src = "images/subnav_masonry_a.gif"
   img7.src = "images/subnav_pavingBrick_a.gif";
   img8.src = "images/subnav_tools_a.gif"         
}


function roll(img_name1, img_src1, img_name2, img_src2)
   {
   document[img_name1].src = img_src1;
   document[img_name2].src = img_src2;
   }