story, UI, html

Go with a briefer alternative that moves you toward something real. Write a one page story about what the app needs to do. Use plain language and make it quick. If it takes more than a page to explain it, then it's too complex. This process shouldn't take more than one day. Then begin building the interface — the interface will be the alternative to the functional spec. Draw some quick and simple paper sketches. Then start coding it into html. Unlike paragraphs of text that are open to alternate interpretations, interface designs are common ground that everyone can agree on. Confusion disappears when everyone starts using the same screens. Build an interface everyone can start looking at, using, clicking through, and "feeling" before you start worrying about back-end code. Get yourself in front of the customer experience as much as possible.