No matter how much a game is tested, bugs will still slip through. The error log provides a centralized location to store all the runtime errors generated in your game, to keep you informed about the state of your game.
Each game has a dedicated error log that you can browse from the admin panel, and a graph over errors reported the last two weeks provides a quick look at the state and development of your game.
The error log stores errors reported from multiple sources. There is a source for each client library and one for each multiplayer roomtype created for a game, and new sources can be introduced on the fly.
Errors can be be filtered by source, grouped by message or stacktrace, and sorted by how recent or how common they are. This makes spotting trends and patterns easy, and makes it painless to know which errors are the most important to fix first.
Uncaught exceptions in serverside code and in the usage of client APIs such as ActionScript 3 are automatically saved in the error log. So without doing anything special, most errors will be caught and saved to the error log.
In addition to automatically saving uncaught exceptions, the APIs also provide methods to submit errors from any place in the game, both client and serverside. This is great for tracking down and debugging those hard to find edge cases that don't manifest themselves with exceptions.