When you set site maintenance to offline, you lose the link to you login form as well. To get the login form, you need to do the following:

http://www.mysite.com/q=user
 or
http://www.mysite.com/user

Do not replace the word user with your username.

If this doesn’t work, log into you database and type the following SQL commands.

UPDATE variable SET value = 's:1:"0";' WHERE name= 'site_offline';
DELETE FROM cache WHERE cid = 'variables';

If you lost your mysql password, go to your drupal installation directory. Then navigate to sites/default. You should see a file by the name of settings.php. Open this file and look for a line which looks like the following.

mysql://username:password@localhost/databasename

Then type the following:

mysql -u username -p databasename

You will be prompted for you password. Once logged in type the SQL commands listed above.

By master