var xPos = 300;
var yPos = 200; 
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;
$("fRandom").style.top = yPos;
function changePos() 
{
	width = document.body.clientWidth;
	height = document.body.clientHeight;
	Hoffset = $("fRandom").offsetHeight;
	Woffset = $("fRandom").offsetWidth;
	$("fRandom").style.left = xPos + document.body.scrollLeft;
	$("fRandom").style.top = yPos + document.body.scrollTop;
	if (yon) 
		{yPos = yPos + step;}
	else 
		{yPos = yPos - step;}
	if (yPos < 0) 
		{yon = 1;yPos = 0;}
	if (yPos >= (height - Hoffset)) 
		{yon = 0;yPos = (height - Hoffset);}
	if (xon) 
		{xPos = xPos + step;}
	else 
		{xPos = xPos - step;}
	if (xPos < 0) 
		{xon = 1;xPos = 0;}
	if (xPos >= (width - Woffset)) 
		{xon = 0;xPos = (width - Woffset);   }
	}
function floatstart() 
{
    if($("fRandom"))
    {
        $("fRandom").style.left= xPos;
        $("fRandom").style.top = yPos;
        $("fRandom").style.visibility = "visible";
        interval = setInterval('changePos()', delay);
    }
}
function pause_resume() 
{
    clearInterval(interval);
}

// 根据ID获取页面元素
function $(id)
{	
	return document.getElementById(id);
}
floatstart();