html5 拖动有关问题 _HTML/CSS

html5 拖动问题
在网上看到说的资料说html5可以拖动。但我无论怎么弄都不行。高人指点
<script language="javascript" src="js/jquery-1.4.2.min.js"></script>
<script language="javascript">
function asd()
{
document.ondragover = function(e){

e.preventDefault();

};

document.ondrop = function(e){

e.preventDefault();

};
}
</script>
</head>

<body onLoad="asd()">
<div draggable=”true” id="a">adfadsfadfadfadfadfadafads</div>
</body>
</html>

------解决方案--------------------

HTML code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>jQuery UI Draggable - Default functionality</title>
    <link rel="stylesheet" href="../../themes/base/jquery.ui.all.css">
    <script src="../../jquery-1.7.2.js"></script>
    <script src="../../ui/jquery.ui.core.js"></script>
    <script src="../../ui/jquery.ui.widget.js"></script>
    <script src="../../ui/jquery.ui.mouse.js"></script>
    <script src="../../ui/jquery.ui.draggable.js"></script>
    <link rel="stylesheet" href="../demos.css">
    <style>
    #draggable { width: 150px; height: 150px; padding: 0.5em; }
    </style>
    <script>
    $(function() {
        $( "#draggable" ).draggable();
    });
    </script>
</head>
<body>

<div class="demo">

<div id="draggable" class="ui-widget-content">
    <p>Drag me around</p>
</div>

</div><!-- End demo -->



<div class="demo-description">
<p>Enable draggable functionality on any DOM element. Move the draggable object by clicking on it with the mouse and dragging it anywhere within the viewport.</p>
</div><!-- End demo-description -->

</body>
</html>