Check out example codes for "css push div down". It will help you in understanding the concepts better.

Code Example 1

<style>
 div{border:1px solid red}
 #container{height:1000px;}
 #inner-container{position:absolute;bottom:0px;}
 .inner {height:200px;width:200px;margin:5px;;
</style>


<div id="container">
 <div id="inner-container">
  <div class="inner"></div>
  <div class="inner"></div>
  <div class="inner"></div>
 </div>
</div>

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