title: How to fix the jQuery 1.8 “Syntax error, unrecognized expression” error?
body: <pre><code>&lt;script type="text/javascript"&gt;
  $(function(){
      $(".user_ava").click(function() {
          $("div:.userMenu",this ).animate({
              height: ["toggle", "swing"],
              opacity: "toggle"
          }, 200, "linear");
      });
  });
  &lt;/script&gt;
  </code></pre>
  
  <p>Error: message ( Uncaught Error: Syntax error, unrecognized expression: :.userMenu  )</p>