window.onload= function(){

var oDiv = document.getElementsByTagName('div')[0];

var timer = null;

var speedX = 0;

var speedY = 0;

var lastX = 0;

var lastY = 0;

oDiv.onmousedown= function(ev){

var oEv = ev || event;

var disX = oEv.clientX-oDiv.offsetLeft;

var disY = oEv.clientY-oDiv.offsetTop;

document.onmousemove=function(ev){

var oEv = ev || event;

oDiv.style.left = oEv.clientX-disX+"px";

oDiv.style.top = oEv.clientY-disY+"px";

speedX = oDiv.offsetLeft - lastX;

speedY = oDiv.offsetTop - lastY;

lastX = oDiv.offsetLeft;

lastY = oDiv.offsetTop;

};

document.onmouseup=function(){

document.onmousemove=document.onmouseup=null;

oDiv.releaseCapture && oDiv.releaseCapture();

move();

};

oDiv.setCapture && oDiv.setCapture();

return false;

};

function move(){

var H = document.documentElement.clientHeight;

var W = document.documentElement.clientWidth;

clearInterval(timer);

timer = setInterval(function(){

speedY+=3;

var t = oDiv.offsetTop+speedY;

var l = oDiv.offsetLeft+speedX;

if(t>=H-oDiv.offsetHeight){

speedY *= -0.8;

speedX *= 0.8;

t=H-oDiv.offsetHeight;

}else if(t<=0){

speedY *= -0.8;

speedX *= 0.8;

t=0;

};

if(l>=W-oDiv.offsetWidth){

speedX *= -0.8;

speedY *= 0.8;

l = W-oDiv.offsetWidth;

}else if(l<=0){

speedX *= -0.8;

speedY *= 0.8;

l = 0;

}

oDiv.style.left = l + "px";

oDiv.style.top = t + "px";

if(Math.abs(speedX) < 1){

speedX = 0;

}

if(Math.abs(speedY) < 1){

speedY = 0;

}

if(speedX == 0 && speedY == 0 && t == H - oDiv.offsetHeight ){

clearInterval(timer);

}

}, 30);

};

};