html 表格head部分不动 body部分滚动，格宽同增长

<style>

.table{    width: 100%;    border-collapse:collapse;    border-spacing:0;}

.table thead{display: block; width: 100%; background: #ddd;} .table tbody{display: block; height:70px; overflow: auto; width: 100%; border: 1px solid #ddd;} .table td,.table th { width: 200px; border-bottom: none; border-left: none; border-right: 1px solid #CCC; border-top: 1px solid #DDD; padding: 2px 3px 3px 4px } .table tr{ border-bottom: 1px solid #B74; } </style>

<table class="table">
                <thead>
                <tr>
                    <th>header</th>
                    <th>header two</th>
                    <th>header two</th>
                    <th>header two</th>
                    <th>header two</th>
                    <th>header two</th>
                </tr>
                </thead>
                <tbody class="M_scrollBar">
                <tr>
                    <td>fuck 1</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                </tr>
                <tr>
                    <td>fuck 1</td>
                    <td>fuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>kfuc<br>k 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                </tr>
                <tr>
                    <td>fuck 1</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                </tr>
                <tr>
                    <td>fuck 1</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                    <td>fuck 2</td>
                </tr>
                </tbody>
            </table>