title: Aligning an input to a divs center
body: <p>Let's say I have this code</p>
  
  <pre><code>&lt;div id="content1" width="400px" height="100px"&gt;
  &lt;input type="text" id="znamkyInput"&gt;
  &lt;/div&gt;
  
  &lt;div id="content2" width="400px" height="100px"&gt;
  &lt;input type="text" id="znamkyInput"&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And I want the input to be <strong>vertically centered</strong> into the center of the div. How can I do that?</p>