I have a problem in styling , in Some case parent node/div do not include height of their child node . If any one had this problem , then please give reason . 

e.g. 

```
#id{
position:relative;
background:red;
}
.spacer{
  height:40px;
  position:relative;
}
<div id="x">
<div class="spacer" style="float:left;"></div>
<div class="spacer" style="float:left;"></div>
</div>

```

In `my` case `height of X node is something different than 80px` (less than 80px). Why this is happening ?

I have lot of code so i can't post all those . Please give any reason .