firefox 对相对定位的TD元素渲染错误

<!DOCTYPE html>
<html>
    <head>
        <title></title>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <style>
            *{
                margin:0px;
                padding: 0px;
            }
            html{
                width:100%;
                height:100%;
            }
            body{
                width:100%;
                height:100%;
            }
            
            .testTable{
                table-layout: fixed;
                border-collapse:collapse;
                width:400px;
                height: 400px;
                border:1px solid blue;
            }
            .testTable td{
                border:1px solid blue;
            }
            .testTable td.testTd {
              position: relative;
              
            }
            .testDiv{
                width:100%;
                height:100px;
                position: absolute;
                bottom: 0px;
                background: red;
            }

</style>
        <script>

</script>
    </head>
    <body >
      
        <table class='testTable'>
            <tr>
                <td class='testTd'>
                    <div class='testDiv'></div>
                </td>
            </tr>
              <tr>
                <td>
                    
                </td>
            </tr>
        </table>

</body>
</html>

firefox22下红争部分竟然以窗口做基准计算！