Example of An Online Drupal Site

This is the usual situation where you can easily log into your administrator account and modify the settings to your account.
Example of An Off-line Drupal Site

If you are reading this tutorial, you are likely faced with this situation...no login. Do not panic! There is a simple solution!
www.mysitesurl.com/?q=user

Just type, ?q=user after your site's root url, e.g. www.mysitesurl.com/?q=user, and this will get you to the hidden login page.
Access Site Maintenance Section

Go to the Site Maintenance Section by clicking on Operating in off-line mode
Set to Online

Pretty simple here. Just set it to Online and save.
Mission Accomplished

You can check your site now and see that it is back online!