title: Making 'file' input element mandatory (required)
body: <p>I want to make (an HTML) 'file' input element mandatory: something like</p>
  
  <pre><code>&lt;input type='file' required = 'required' .../&gt;
  </code></pre>
  
  <p>But it is not working.</p>
  
  <p>I saw this <a href="http://www.w3.org/TR/html-markup/input.file.html#input.file.attrs.required" rel="noreferrer">WW3</a> manual which states 'required' attribute is new to HTML 5. But I am not using HTML 5 in the project I am working which doesn't support the new feature.</p>
  
  <p>Any idea?</p>