关于浏览器不兼容flex布局的问题
display: -webkit-box; /* OLD - iOS 6-, Safari 3.1-6 */
display: -moz-box;/* OLD - Firefox 19- (buggy but mostly works) */
display: -ms-flexbox;/* TWEENER - IE 10 */
display: -webkit-flex;/* NEW - Chrome */
display: flex;/* NEW, Spec - Opera 12.1, Firefox 20+ */
