Edit in JSFiddle

$(document).ready(function() {
	$("div").animate({
				left:'+=300px',
    }, 8000); 
});

<div>BOX</div>

div{
    background-color:#333;
    Color:#fff;
    width:50px;
    height:50px;
    position:absolute;
    left:0px;
    top:0px;
}