```
  <div class="box small">
    <p>Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas.</p>

    <div class="detail"> for more info click below</div>
    <div class="read-more"> click</div>
 </div>

```

**Css** 

```
.detail{
      position: relative;
}
.detail:after{
  content: "";
  display: block;
  position: fixed; /* could also be absolute */ 
  bottom: 0;
  left: 0;
  height: 100%;
  width: 20%;
  z-index: 10;
  background-color: rgba(0,0,0,0.2)
}  

```

I wan to add a background for these two divs : 

```
 <div class="detail"> for more info click below</div>
 <div class="read-more"> click</div>  

```

I can't add a wrapper div , so i'm using overlay Technique: 

[Demo](http://jsfiddle.net/g5jEr/989/) 

How can i relative overlay to parent box ?