title: Why are HTML forms sometimes cleared when clicking on the browser back button
body: <p>I am sure everybody knows that behaviour. You fill in a form on the web, and you submit it. After the submission you recognize that you filled in some wrong data. So, you click on the browsers back button. Then, sometimes the form still have the data you entered <em>(what you are hoping in this situation)</em> and sometimes not.</p>
  
  <p>I couldn't find any connection when it is cleared and when not.</p>
  
  <p>Some answers i found on the internet / stackoverflow:</p>
  
  <ul>
  <li>on https connections, forms are always cleared</li>
  <li>when using dynamic websites with sessions, forms are always cleared</li>
  </ul>
  
  <p>But both of them are definatly wrong. I have seen sites (like one of my own) that does keep the form-data after the browser back <strong>and</strong> are using https <strong>and</strong> are using sessions.</p>
  
  <p>So please: can anybody explain me how browsers are handling this stuff?</p>
  
  <p>By the way: my task is it to make sure that the form data is <strong>not</strong> cleared.</p>