title: Can I use robots.txt to block certain URL parameters?
body: <p>Before you tell me 'what have you tried', and 'test this yourself', I would like to note that <code>robots.txt</code> updates awfully slow for <del>my site</del>any site on search engines, so if you could provide theoretical experience, that would be appreciated.</p>
  
  <p>For example, is it possible to allow:</p>
  
  <pre><code>http://www.example.com
  </code></pre>
  
  <p>And block:</p>
  
  <pre><code>http://www.example.com/?foo=foo
  </code></pre>
  
  <p>I'm not very sure.</p>
  
  <p>Help?</p>