지정한 가로 길이를 넘어갈 경우 자동 줄바꿈

word-wrap: break-word; /* Internet Explorer 5.5+ */
white-space: pre-wrap; /* css-3 */
white-space: -moz-pre-wrap; /* Mozilla, since 1999 */
white-space: -pre-wrap; /* Opera 4-6 */
white-space: -o-pre-wrap; /* Opera 7 */
word-break:break-all;