从网上找的,忘了作者链接,若作者看到此文,请留言链接,我将补上

PRE {
    overflow: auto;
    overflow-y: hidden;
    background-color: grey;
    font-size: 12px;
    width: 95%;
    line-height: 16px;
    font-family: "Courier New", FixedSys;
    color: #555;
    background: #fafafa;
    border-top: 1px solid #ccc;
    border-bottom: 1px solid #ccc;
    border-left: 15px solid #ccc;
    border-right: 1px solid #ccc;
    padding: 0 5px;
    margin: 0 0 20px;
}

效果看此处即可