响应式布局

/*小屏幕*/
@media screen and (max-width: 768px) {}
/*平板*/
@media screen and (min-width: 768px) and (max-width: 992px){}
/*中等屏幕*/
@media screen and (min-width: 992px) and (max-width: 1200px){}
/*大屏幕，或者宽屏*/
@media screen and (min-width: 1200px) {}