From Jakob Nielsen's "Response Time Limits": "10 seconds is about the limit for keeping the user's attention focused on the dialogue. For longer delays, users

From Jakob Nielsen's "Response Time Limits": "10 seconds is about the limit for keeping the user's attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will then not know what to expect." Read on crystal clear explanation of why this is and how to build around if load time is a must: http://www.useit.com/papers/responsetime.html http://www.useit.com/papers/responsetime.html