Reason
The creators of MapleStory take the game offline for to add new content. Nexon uploads new content, including changes to maps and monsters and cash shop items, that will become active when the company brings the game back online. Nexon took MapleStory down to introduce the Big Bang plot changes, for example. This process is known as patching. The company may also take the game offline for unexpected errors that may arise from hardware issues or changes introduced by the patch itself.
Significance
When MapleStory is offline, you cannot play it to level up your character, complete quests or gain new items. If you are signed on before the game goes offline, you will be forced to sign off. You could lose data due to the game closing, especially if you are working on timed quests. You should make sure to log off before the game forces you to do so to ensure that any new skills, items or money save to your account. After the game comes back online, you will have to download the updates to your computer. This process will take several moments, depending on the gravity of the changes and the speed of your Internet connection.
Update Alerts
MapleStory will display an alert if you are signed on and the game is intended to go online. This alert will tell you how soon the update will occur -- for example, in thirty minutes -- and update until the game forces you to sign off. the MapleStory website will also alert players of planned outages within the "Maintenance" tab on the news page. Prior to the game going offline, these pages will show the date and estimated outage time frame. After the patch, the posts will notate changes and addition to the game content.
When Updates Occur
Nexon will take MapleStory offline for large plot changes that surround events like the Big Bang and Ascension. MapleStory also goes offline before major holiday seasons like Christmas and Thanksgiving, so that the creators can update with seasonal content. Every year, Nexon hosts a Maple anniversary events with contests, new items and special monsters, like the cake monster. MapleStory will go offline in early late April as the game server updates to include this temporary content. However, many outages are unscheduled. For instance, there were five instance of unscheduled server maintenance in June 2011.