public static function header_output() {
  ?>
  <!--Customizer CSS-->
  <style type="text/css">
       <?php self::generate_css('#site-title a', 'color', 'header_textcolor', '#'); ?>
       <?php self::generate_css('body', 'background-color', 'background_color', '#'); ?>
       <?php self::generate_css('a', 'color', 'link_textcolor'); ?>
  </style>
  <!--/Customizer CSS-->
  <?php
}

public static function generate_css( $selector, $style, $mod_name, $prefix='', $postfix='', $echo=true ) {
  $return = '';
  $mod = get_theme_mod($mod_name);
  if ( ! empty( $mod ) ) {
     $return = sprintf('%s { %s:%s; }',
        $selector,
        $style,
        $prefix.$mod.$postfix
     );
     if ( $echo ) {
        echo $return;
     }
  }
  return $return;
}