<style>
.test{width:300px; padding:30px 20px; margin-left:60px; margin-top:100px; background:#beceeb; position:relative;}
.test span{width:0; height:0; font-size:0; overflow:hidden; position:absolute;}
.test span.bot{
    border-width:20px; 
    border-style:solid; 
    border-color:#ffffff #beceeb #beceeb #ffffff; 
    left:-40px; 
    top:40px;
}
.test span.top{
    border-width:10px 20px; 
    border-style:dashed solid solid dashed; 
    border-color:transparent #ffffff #ffffff transparent; 

    left:-40px; 
    top:60px;
}
.fly1{
 
 border-width:20px;
 border-style: solid solid solid solid;
 border-color:#fff #beceeb #beceeb #fff;
 position: absolute;
  left: 100px;
  top: -40px;

}
.fly2{
 border-width:20px 10px;
 border-style:solid;
 border-color:transparent #ffffff #ffffff transparent;
 position: absolute;
 left:140px;
 top: -40px;
}
</style>
<div class="test">
    <div class="fly1"></div>
    <div class="fly2"></div>
    <span class="bot"></span>
    <span class="top"></span>
    CSS “边框法”实现气泡对话框效果一

</div>