var draggable = function(element) {
    element.addEventListener('mousedown', function(e) {
        e.stopPropagation();

        // if the current target is different (in the case of a child node), don't drag.
        // you can customize this to specify types of children which prevent dragging
        if (e.target != element)
            return;

        var offsetX = e.pageX - element.offsetLeft;
        var offsetY = e.pageY - element.offsetTop;

        function move(e) {
             element.style.left = (e.pageX - offsetX) + 'px';
             element.style.top = (e.pageY - offsetY) + 'px';
        }
        function stop(e) {
            // remove the event listeners on the document when not dragging 
            document.removeEventListener('mousemove', move);
            document.removeEventListener('mouseup', stop)
        }

        document.addEventListener('mousemove', move)
        document.addEventListener('mouseup', stop)

    })  


}

function init() {
  var ele = document.getElementById('ele');
  draggable(ele)
}

これは一部の IE バージョンでは機能しない場合がありますが、必要な修正を追加できるはずです。ここにフィドルがありますhttp://jsfiddle.net/seKbz/2/