title: NS_ERROR_XPC_BAD_CONVERT_JS
body: <p>I'm getting this error after trying to "appendChild" to an element that was just created (in for loop).<br>
  What does this error mean?<br>
  I suppose it's not possible to append sth. to an element that doesn't really exist in DOM.<br>
  How do I fix it?<br>
  "innerHTML" works, but I don't think it's really clean and proper way to do it.</p>