title: Jquery error: Syntax error, unrecognized expression
body: <p>This is my HTML:</p>
  
  <pre><code>&lt;div class="dropdown-text" id="dropdownopen" onclick="dropdownopen(0)"&gt;
      &lt;div class="inside"&gt;+ Show Content&lt;/div&gt;
  &lt;/div&gt;
  
  &lt;div class="dropdown" id="dropdownnum(0)"&gt;
       &lt;div class="inner"&gt;INSERT DROPDOWN CONTENT IN HERE&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>And here is my JS (Jquery):</p>
  
  <pre><code>function dropdownopen(param) {
      $('#dropdownnum('+param+')').fadeOut(300);
  }
  </code></pre>
  
  <p>The #dropdownnum(0) div is display:none; by default, so this should work, but I get the error: </p>
  
  <p>Uncaught Error: Syntax error, unrecognized expression: #dropdownnum(0).</p>