title: jQuery attribute selectors: How to query for an attribute with a custom namespace
body: <p>Suppose I have a simple XHTML document that uses a custom namespace for attributes:</p>
  
  <pre><code>&lt;html xmlns="..." xmlns:custom="http://www.example.com/ns"&gt;
      ...
      &lt;div class="foo" custom:attr="bla"/&gt;
      ...
  &lt;/html&gt;
  </code></pre>
  
  <p>How do I match each element that has a certain custom attribute using jQuery? Using</p>
  
  <pre><code>$("div[custom:attr]")
  </code></pre>
  
  <p>does not work. (Tried with Firefox only, so far.)</p>