<p style="background:#000; width:100px; color:#F00; word-wrap:break-word" data-mce-style="background: #000; width: 100px; color: #f00; word-wrap: break-word;">haha 555555555555555555555555555555555
</p>

<p style="background:#000; width:100px; color:#F00; margin-top:10px; word-break:break-all" data-mce-style="background: #000; width: 100px; color: #f00; margin-top: 10px; word-break: break-all;">haha 555555555555555555555555555555555
</p>

　　word-break:break-all;不但让单词从溢出变折行，还让上面未被填充的区域补齐，反正我觉得吧，比word-wrap好用点..

天道酬勤