var c = 1;

/* Preloading images */
var image1 = new Image();
image1.src = "images/w1.JPG";
var image2 = new Image();
image2.src = "images/w2.JPG";
var image3 = new Image();
image3.src = "images/w3.JPG";
var image4 = new Image();
image4.src = "images/w4.JPG";

function disp_img(w)
   {
   if (c == 5)
      {
      c = 1;
      }
   var img_src = "images/w" + c + ".JPG";
   document.wc.src = img_src;
   c++;
   }
t = setInterval("disp_img(c)", 3000);