Code
<script language="JavaScript">
<!--
var xoff = 400;
var yoff = 300;
var inc = -5;
function move() {
yoff += inc;
ball.top = yoff;
ball.left = xoff;
if (yoff<= 150) {inc = 5;}
if (yoff>= 300) {inc = -5;}
setTimeout("move()", 50);
}
-->
</script>
</head>
<body>
<div id="ball" style="position:absolute;width:10px; height:10px"><img src="ССЫЛКА КАРТИНЫ" border=0></div>
<script language="JavaScript">
<!--
var NN = (navigator.appName == "Netscape" && parseInt(navigator.appVersion) >= 4);
var ball = (NN) ? document.ball : document.all.ball.style;
move();
-->
</script>