If you are a member of the Apple Developer Connection, go to:
http://developer.apple.com/bugreporter/
If you are not a member of the Apple Developer Connection, you have two other options:
Customer Quality Feedback (CQF)
CQF is an Apple program that provides end-users with an opportunity to influence the development of Apple hardware and software products worldwide. This includes comments about the human interface, desired features, performance, and compatibility with Apple and third-party products in time to help improve the shipping product. CQF project managers represent these customers via their feedback throughout the development cycle, prior to the release of new products.
Visit our Customer Quality Feedback (CQF) site at:
http://www.cqf.apple.com/
Apple Discussions
If you have a question about an issue you experience with an Apple product, or feedback you would like to offer to Apple, this is the place to post it. For more information, see:
http://discussions.info.apple.com/.