title: How to get position from top in pixel of an element?
body: <p>I have one <code>UL</code> element which has 5 <code>LI</code> elements:</p>
  
  <pre><code>ul{
      width: 200px;
      height: 100%;
      padding: 0;
      margin: 0;
      overflow-y: auto;
      overflow-x: hidden;
      list-style: none;
      margin-left: 3px;
  }
  
  li{
      position: relative;
      height: 50px;
      width: 193px;
      left: 0;
      right: 0;
      margin: 10px 0;
      cursor: pointer;
  }
  </code></pre>
  
  <p>I'd like to get the <strong>top</strong> pixel value for every <code>LI</code> from the <code>UL</code> top, but when I use this code:</p>
  
  <pre><code>$('ul li').each(function(){
      console.log($(this).css('top'));
  });
  </code></pre>
  
  <p>it just shows me this : <code>'auto'</code>, why?</p>