Over the last 10 years we have been doing this, on large scale projects I designed for the USAF and smaller websites we have found that getting approval at set milestones is the only way to get then site up and running. There are several important areas that need approval prior to moving to the next step. This speeds overall development and ensures that the customer is both happy with the website and meets his goals.
1. Basic colors, fonts, navigation layout (links), logo placement, and basic functioning.
2. Content pages layout
3. Database functioning (if website is DB driven)
4. Content added to site
5. E-commerce functioning
6. Website acceptance
All milestones require customer review and acceptance pior to moving to the next step. Going back and making changes to items already accepted will cause delays and depending on the change may incur additional cost.
For example, if you are at website acceptance and want to change the main font color, this will probably require all new graphics and page titles. More time = More cost.