CSS opacity属性

CSS opacity属性

top
middle
bottom

<div id="top">top</div>
<div id="middle">middle</div>
<div id="bottom">bottom</div>
<style>
  #top,#middle,#bottom
  {
    border-color: gray;
    border-width: 1px;
    border-style: solid;
    background-color: blue;
    color: white;
    text-shadow: 3px 3px 1px black;
    box-shadow: 3px 3px 5px black;
  }

  
  #top
  {
    0=0% ~ 1=100%
    opacity: 0.5;
  }
  
  #middle
  {
    opacity: 0.5;
  }
  
  #bottom
  {
    opacity: 0.5;
  }
</style>