I want to show the image in the center of the page using jquery , in asp.net app.

<script type="text/javascript" language="ecmascript">

      function ShowBiggerImage(obj) {

          document.getElementById("imgdiv").style.visibility = "visible";
          document.getElementById("imgdiv").innerHTML = "<img src='" + obj.src + "'+'width=640 height=480' >";
          document.getElementById("imgdiv").style.left = event.clientX;
          document.getElementById("imgdiv").style.top = event.clientY;

          document.getElementById("imgdiv").style.zIndex = "0";

      }
      function ShowDefaultImage(obj) {
          document.getElementById("imgdiv").innerHTML = "";
          document.getElementById("imgdiv").style.visibility = "hidden";
      }


  </script>