title: Mark selected days in jQuery UI datepicker
body: <p>I'm using jQuery UI's datepicker (http://docs.jquery.com/UI/Datepicker).</p>
  
  <p>It sounds like it should be possible to mark certain days by providing a <code>beforeShowDay</code> function (http://docs.jquery.com/UI/Datepicker#event-beforeShowDay). But I can't get the CSS right for this. I'd like to make the background green for some days.</p>
  
  <p>This is the JavaScript I have this far:</p>
  
  <pre><code>$(function() {    
      $('.date').datepicker({
          dateFormat: 'yy-mm-dd',
          firstDay: '1',
          showOtherMonths: 'true',
          beforeShowDay: daysToMark
      });
  });
  
  function daysToMark(date) {
      if (date.getDate() &lt; 15) {
          return [true, 'markedDay', ""];
      }
  
      return [true, '', ""];
  }
  </code></pre>
  
  <p>And this is the css:</p>
  
  <pre><code>.markedDay {
      background-color: green;
  }
  </code></pre>
  
  <p>But nothing changes. What am I doing wrong?</p>