When a vendor is designing a website for a client - an organisation with Business Analysts and Project Managers assigned to the project - we need to provide concepts/wireframes and with annotations, reference Business Requirements (e.g. a sign-in link must be visible on all pages OR "Advertisement A" must be above-the-fold for screen resolutions 1280x1024 (60% of visitors)).

I want to make sure that when the question is asked, "Why is that news widget inserted in that position of the page?" that there is no scrambling around for rationale. I want to quickly identify:

• What Business Requirement this element refers to
• What interview/study supports this element being in this location
• What assumptions must the client be aware about the element being in this location
• Where are the variations that each element may inherit

What is the standard of validating Business Requirements? Is it typically through a spreadsheet, a meeting?