public function executeCss()
 {
     // this retrieves the filename of the latest public CSS file
     $publicCssFilename = shell_exec('ls -1 -tr ' . sfConfig::get('sf_web_dir') . '/css/all_public*');
     $publicCssFilename = trim(basename($publicCssFilename));
     $mainHttpHost = PcUtils::mainUrlFromOtherApplication();
     $this->publicCssUrl = 'http://' . $mainHttpHost . '/css/' . $publicCssFilename;
 }