title: how to center align a box to the window size?
body: <p>I would like to center align a div(<code>cen</code>) which is inside another div(<code>imp</code>) </p>
  
  <p>Here is the code example</p>
  
  <pre><code>.imp
  {
          width:100%;
          height:100%;
          background-color: black;
          position: fixed;
          top:0;
          bottom:0;
  }
  </code></pre>
  
  <p>above is the main div now the div which should be center is given below</p>
  
  <pre><code>    .cen
     {
      margin-left:auto;
      margin-right:auto;
      padding:5px;
      width:auto;
      height:auto;
  
     }
  </code></pre>
  
  <p>Here is my question how to align <code>.cen</code> to middle of the browser?
  Having margin-left:auto; margin-right:auto; brings to center but not from the top.I have given top to 50% and left 50% then also i can't align it center because the content inside <code>.cen</code> bigger so it appears bottom right of the window. Any clue or idea?  </p>