Use Gravatars in Your Application

function show_gravatar($email, $size, $default, $rating)
{
    echo '<img src="http://www.gravatar.com/avatar.php?gravatar_id='.md5($email).
        '&default='.$default.'&size='.$size.'&rating='.$rating.'" width="'.$size.'px"
        height="'.$size.'px" />';
}