How can get my site out of maintenance mode?
There is a few things you can try.

1. Using drush

Go to root of the website and run this drush commands one by one:

drush vset maintenance_mode 0
drush cc all


2. Using database query

Go to phpmyadmin and run this db statement in order to update the "maintenance_mode" property in the variable table to "i:0;":

UPDATE `variable` SET `value` = 'i:0;' WHERE `name` = 'maintenance_mode';


3. Login as admin programatically

Make copy of the index.php file and call it what every want (maintenance.php for example) and at the end of the file replace

menu_execute_active_handler();


with

global $user;
$user = user_load(1);
drupal_session_regenerate();
drupal_goto('user');


go to that file (like [your_website]/maintenance.php), after that just disable maintenance mode and don't forget to remove this file after you finish.

4. Manually set maintenance_mode variable in index.php

Edit index.php file and put

variable_set('maintenance_mode', 0);


just before

menu_execute_active_handler();


5. Configure maintenance mode in settings.php file

At the end of your settings.php file put

$conf['maintenance_mode'] = 0;