[This is preliminary documentation and subject to change.]
Requirement (Designed for Microsoft® Windows® Logo)
Your application must provide notifications to other software of the locations of the keyboard focus, either by moving the system caret or by using Microsoft® Active Accessibility™.
This requirement enables the use of accessibility aids such as the screen magnification accessory included with Windows 98 and the Active Accessibility SDK.
Development tools are temporarily exempt from the requirement to expose the keyboard focus. Vendors should be aware that this exemption will be removed in the next update of the Logo guidelines.
Pretesting Exposure of Keyboard Focus.
http://microsoft.com/enable/ for accessibility guidelines for application developers.