how to add html/ccs element s inside drupal mail function

I am developing function that send a email to user..,and i want to add some html.css styleing to the email how can i achive that folllwing is my code i tried

function zgcrons_mail ($key, &$message, $params) {
  switch ($key) {
  case 'mymail':
    // Set headers etc
    $message['to'] = $usermail;
    $message['subject'] = t('Your Donation Statues ');
    $message['body'][] = '<table width="100%" cellspacing="0" cellpadding="10" border="0">
    <tbody>
    <tr>
        <td valign="middle" style="border-collapse:collapse;border:0" colspan="2">
            <div style="color:#585858;font-family:Georgia;font-size:12px;line-height:125%;text-align:center">&nbsp;
                <a target="_blank" style="color:#ee3524;font-weight:bold;text-decoration:underline" href="http://www.twitter.com/ZealousGood/">follow on Twitter</a> | 
                <a target="_blank" style="color:#ee3524;font-weight:bold;text-decoration:underline" ref="http://www.facebook.com/ZealousGood2011">friend on Facebook</a>
            </div>
        </td>
    </tr>
    <tr>
        <td width="372" valign="top" style="border-collapse:collapse">
            <div style="color:#585858;font-family:Georgia;font-size:12px;line-height:125%;text-align:center">
                <em>Copyright &copy; 2012 Zealous Good, All rights reserved.</em> 
                <br>
            </div>
        </td>
    </tr>
    </tbody></table>';
  break;
  }
}
drupal_mail('zgcrons', 'mymail',$usermail, $language, $params = array('username' =>'John Potato'), $from = NULL, $send = TRUE);