var xPos = 20;
var yPos = document.body.clientHeight;
var step = 1;
var delay = 5;
 var height = 0;
 var Hoffset = 0;
 var Woffset = 0;
 var yon = 0;
 var xon = 0;
 var pause = true;
 var interval;dd.style.top = yPos;
 function changePos() { width = document.body.clientWidth;height = document.body.clientHeight;
 Hoffset = dd.offsetHeight;
Woffset = dd.offsetWidth;
dd.style.left = xPos + document.body.scrollLeft;
dd.style.top = yPos + document.body.scrollTop;
if (yon) {yPos = yPos + step;}
else {yPos = yPos - step;}
if (yPos < 0) {yon = 1;
yPos = 0;}
 if (yPos >= (height - Hoffset)) {yon = 0;
 yPos = (height - Hoffset);}
if (xon) {xPos = xPos + step;}
else {xPos = xPos - step;}
if (xPos < 0) { xon = 1;
xPos = 0;        }
if (xPos >= (width - Woffset)){xon = 0;xPos = (width - Woffset);}}
function start() {dd.visibility = "visible";interval = setInterval('changePos()', delay);}
function pause_resume() {if(pause) {clearInterval(interval);pause = false;}
else {interval = setInterval('changePos()',delay);pause = true;
}}start();