Functional/Technical specifications and web process

Hi all
I have been working on a web project that will use php and Mysql and I intend to use OO design as much as possible and to use three N-Tiers, Data access, Business logic and Presentation GUI layer and as important as the project is the way I implement it using a defined process and sound software engineering methodology is more important to me and I intend to get some help after I finish designing my classes and the database I have reached a stage where I am ready to start writing the functional and technical specifications after I have finished requirements analysis but I still have some ambiguity before I begin:
1-I will write the functional specification from a user’s point of view.
2-The technical specification will serve as the basis for the Server specification, User machine specification, security and such issues
But some questions arise:
Should I include things like this field should be validated on the client side using JavaScript, Should I write stuff like redirect the user to another page on some basis, or use flash here and use Dhtml there in the functional specification?

My application is built around a fantasy soccer game so a lot should be done in the business Tier and it seems to me that after writing the functional specification a database designer should be able to work on the database and the data Tier will not make a problem, the interface tier also could be built but I think that it would be hard to go directly from a functional specification to class design and Implementation it seems that there would still be a missing document that states how the application would work internally.

So what do you think is there some kind of document I am missing out between the functional specification and the class diagrams one that would maybe include things like data structures maybe and such issues?

I would be really be thankful if you can give me some links to some documents such as functional specifications so I can validate my work and it would be really better if I can see some of your works.
I know that I have asked a lot but I appreciate any help or suggestion even if it was little.

Best Regards