title: Magento Service Unavailable Error message
body: <p>In my Magento website, I have received this error message:</p>
  
  <blockquote>
    <p>503 Service Unavailable</p>
  </blockquote>
  
  <p>I am not able to access any PHP files.</p>
  
  <p>Does anyone know what is a reason behind that?</p>