title: How can I prevent users from voting more than one time?
body: <p>I want to prevent users from voting more than one time in my website, I used two methods to do that, but no one do that well !! <br/><br/></p>
  
  <ol>
  <li><strong>using cookie</strong>.<br/>
  <em>the problem</em> : users can delete the cookie and return to vote again and again .. <br/><br/></li>
  <li><strong>using database table.</strong> <br/>
  <em>The problem</em> : users shouldn't forced to register in my website !<br/></li>
  </ol>
  
  <p>So, How i can solve this problem ?</p>