<divclass="main_comment">測試的文字~~~~~`</div>
<divclass="commentBar">回覆框</div>

-----------------------------------------------複製到自己瀏覽器上試試吧------------------------------

.main_comment{
  width:100%;
  position:absolute;
  overflow-y:auto;
  top:0;
  bottom:0;
  -webkit-overflow-scrolling: touch;  /*這句是為了滑動更順暢*/
}
.commentBar{
  width:100%;
  position:absolute;
  bottom:0;
  left:0;
  background:#fff;
  padding:5px;
  z-index:99;
}
 

原文地址

http://www.cnblogs.com/AliceLiu/p/5722935.html