How To Address Magento Error 503 : Service Unavailable?

This specific 503 error message is shown as a result of enabled maintenance on your Magento installation. just in case you have not specifically set the maintenance mode, this error may result as a result of the installation of extensions on your Magento web site through the Magento Connect Manager.

There is a simple solution to removing this error, all you have to do is access the root directory of your Magento installation. You’ll be able to either do this through FTP otherwise you can directly make use of the File Manager service present in your cPanel account. NMavigate to the directory of your Magento web site and in this directory, look for the file – ‘maintenance.flag’. Once you find this file, remove it and your web site will be accessible normally again.