title: Facebook development problem on return canvas url
body: <p>I have an application i.e <code>apps.facebook.com/myappnamegoeshere/</code></p>
  
  <p>Its canvas URL is i.e <code>subdomain.mysite.com</code></p>
  
  <p>When Facebook wants to authenticate me it returns my canvas URL, but it addssomething like this to my URL:</p>
  
  <pre><code>subdomain.mysite.com/amegoeshere/?authtoken=bla bla...
  </code></pre>
  
  <p>My page gives 404 error, naturally.</p>
  
  <p>Does anyone know how to fix this?</p>