$(document).ready(function () {
$('#drag').mousedown(function(){
$(document).mousemove(function(event){
$('#drag').css({'left':event.pageX,'top':event.pageY});
});
});
$(document).mouseup(function(){
$(this).off('mousemove');
$('#drag').css({'left':'','top':''})
});
});
<body>
<div id="drag">
</div>
</body>
#drag {
width: 20px;
height: 20px;
border-radius:10px;
background: #ccc;
position: fixed;
}