Online user assistance is an important part of a product's design and can be supported in a variety of ways, from automatic display of information based on context to commands that require explicit user selection. Its content can be composed of contextual, procedural, explanatory, reference, or tutorial information. But user assistance should always be simple, efficient, and relevant so that a user can obtain it without becoming lost in the interface. This chapter provides a description of the system support to create common online forms of user assistance support and guidelines for implementation. For more information about authoring Help files, see the documentation included in the Microsoft Win32 Software Development Kit (SDK).