H5懸浮返回按鈕,轉載自:https://blog.csdn.net/qq_26817251/article/details/53648685
<div id="dg" onclick="history.back()" style="z-index: 9999; position: fixed ! important; right: 20px; top: 700px;">
<div width="100%" style="position: absolute; right: 0px; top: 0px;">
<img src="images/back.png" >
</div>
</div>