title: How to put magento in maintenance
body: <p>Is it possible to put a magento site under an maintenance flag so that visitors will get a message that the site is under construction?
  I can't find this setting in the admin area.</p>
  
  <p>Another solution will also be welcome.</p>
  
  <p>Any help would be appreciated.</p>
  
  <p>Thank you.</p>