title: XHTML w3c validation error "reference to non-existent ID "xxxxx""
body: <p>For this portion of code </p>
  
  <pre><code>&lt;label for="gender"&gt;I am:&lt;/label&gt;
  &lt;select class="select" name="sex" id="sex"&gt;
    &lt;option value="0"&gt;Gender:&lt;/option&gt;
    &lt;option value="1"&gt;Female&lt;/option&gt;
    &lt;option value="2"&gt;Male&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>W3C Validator giving this error <strong>reference to non-existent ID "gender"</strong></p>
  
  <p>How to solve this?</p>
  
  <p><strong>Edit</strong></p>
  
  <p>Getting here also</p>
  
  <p><strong>reference to non-existent ID "birthday"</strong></p>
  
  <pre><code>&lt;label for="birthday" class="birthday"&gt;Birthday:&lt;/label&gt;
  
  &lt;div class="field_container"&gt; 
  
  &lt;select name="birthday_month" id="birthday_month" class=""&gt;
  &lt;option value="-1"&gt;Month:&lt;/option&gt;
  &lt;option value="1"&gt;Jan&lt;/option&gt;
  &lt;option value="2"&gt;Feb&lt;/option&gt;
  &lt;option value="3"&gt;Mar&lt;/option&gt;
  &lt;/select&gt; 
  &lt;select id="birthday_day" name="birthday_day"&gt;
  &lt;option value="-1"&gt;Day:&lt;/option&gt;
  &lt;option value="1"&gt;1&lt;/option&gt;
  &lt;option value="2"&gt;2&lt;/option&gt;
  &lt;option value="3"&gt;3&lt;/option&gt;
  &lt;/select&gt;
  &lt;select id="birthday_year" name="birthday_year"&gt;
  &lt;option value="-1"&gt;Year:&lt;/option&gt;
  &lt;option value="2010"&gt;2010&lt;/option&gt;
  &lt;option value="2009"&gt;2009&lt;/option&gt;
  &lt;option value="2008"&gt;2008&lt;/option&gt;
  
  &lt;/select&gt;
  &lt;/div&gt;
  </code></pre>