JavaScript兑现浮动窗口

<div id="img" style="position:absolute; left:35px; top:556px; width:120; 

height:172">

<img src="3.jpg" width=100 height=100></img>

</div>

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin

var xPos = 20;

// 图片的起始高度
//var yPos = document.body.clientHeight;
var yPos = 0;

var step = 1;

var delay = 30;

var height = 0;

var Hoffset = 0;

var Woffset = 0;

var yon = 0;

var xon = 0;

var pause = true;

var interval;

img.style.top = 0;

function changePos() {

	width = document.body.clientWidth;

	height = document.body.clientHeight;

	Hoffset = img.offsetHeight;

	Woffset = img.offsetWidth;

	img.style.left = xPos + document.body.scrollLeft;

	img.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() {

	img.visibility = "visible";

	interval = setInterval('changePos()', delay);

}

start();

// End -->

</script>