pre 自动换行

.pre{
    white-space:pre-wrap; /* css3.0 */
    white-space:-moz-pre-wrap; /* Firefox */
    white-space:-pre-wrap; /* Opera 4-6 */
    white-space:-o-pre-wrap; /* Opera 7 */
    word-wrap:break-word; /* Internet Explorer 5.5+ */
}