图片--全局CSS样式

<img src="..." class="img-responsive" alt="Responsive image">
class="img-responsive"表示随着显示大小随便变化，永远都占100%，占满

 

<img src="..." alt="..." class="img-rounded">
<img src="..." alt="..." class="img-circle">
<img src="..." alt="..." class="img-thumbnail">