Essayez-le vous-même - JavaScript Reference ondragstart

<!DOCTYPE HTML>
<html>
<head>
<style>
.droptarget {
    float: left; 
    width: 100px; 
    height: 35px;
    margin: 15px;
    padding: 10px;
    border: 1px solid #aaaaaa;
}
</style>
</head>
<body>

<p>This example demonstrates how to assign an "ondragstart" and "ondragend" event to a p element and an "ondragover" and "ondrop" event to a div element.</p>

<p>Drag the p element back and forth between the two rectangles:</p>

<p style="clear:both;"><strong>Note:</strong> drag events are not supported in Internet Explorer 8 and earlier versions or Safari 5.1 and earlier versions.</p>

function dragEnd(event) {
    document.getElementById("demo").innerHTML = "Finished dragging the p element.";
}

/* Events fired on the drop target */
function allowDrop(event) {
    event.preventDefault();
}

function drop(event) {
    event.preventDefault();
    var data = event.dataTransfer.getData("Text");
    event.target.appendChild(document.getElementById(data));
}
</script>

</body>
</html>