title: Absolute positioned eleement by no positioned ancestor set itself by monitor no body
body: <p>Absoloute positioned element (input) place in bottom of monitor no body.</p>
  
  <p>If i add a relative position to body, input place in bottom of body!</p>
  
  <p><strong>why?</strong></p>
  
  <pre><code>&lt;body&gt;
  
       &lt;input type="button" value="click" style="position:absolute;bottom:0;" /&gt;
  
       &lt;div style="height:500px;background-color:red;"&gt;&lt;/div&gt;
       &lt;div style="height:500px;background-color:blue;"&gt;&lt;/div&gt;
       &lt;div style="height:500px;background-color:green;"&gt;&lt;/div&gt;
       &lt;div style="height:500px;background-color:yellow;"&gt;&lt;/div&gt;
       &lt;div style="height:500px;background-color:pink;"&gt;&lt;/div&gt;
  
  &lt;/body&gt;
  </code></pre>