var a=-50;
var width=800; height=600;

function clientNav() {
  if(navigator.appName.indexOf("Netscape") != -1) {
             if (parseInt(navigator.appVersion) == 4) {
                window.setTimeout('move_nc()', 20);

             } else if (parseInt(navigator.appVersion) >=5) {
                window.setTimeout('move_w3c()', 10);
               }

             } else  {
               if ((parseInt(navigator.appVersion) >= 4) && (navigator.appName.indexOf("Microsoft") != -1)) {
                  window.setTimeout('move_ie()', 20);
               }
  }
}

  function move_nc() {

  a+=1;

    if (a<550) {
    window.document.gra.left=a-40;
    window.setTimeout('move_nc()', 10);
    }
  }

  function move_w3c() {

  a+=1;
  var x1 = document.getElementById("gra").style;

    if (a<540) {
    x1.left=a-20;
    window.setTimeout('move_w3c()', 10);
    }
  }

  function move_ie() {

  a+=2;

    if (a<550) {
    gra.style.left=a-40;
    window.setTimeout('move_ie()', 10);
    }
}