What should be in a web design spec?

[MOH]

If I'm putting together a spec for advertising a web design job, what should I include in it?

It's an e-commerce site, if that makes a difference.

I'm thinking:
- overall look and feel I'm trying to achieve
- guide to preferred colours, if any
- any font style preferences
- a list of the various pages I'll need done, examples if possible of sites I like and don't like for each page
- maybe a rough layout of how I envision each page? Or should I leave that to the designer?
- might need a logo too, in which case I guess I'll need guidelines for that

What should I be asking for in terms of deliverables? I should be able to do the CSS myself, so I'd really just be looking for screen mockups, and any images for buttons and icons. If I'm getting a logo, it'll be used in print as well as on the web, so I presume there's standard formats for that I should be asking for too?

I figure if I put as much information as possible in at the start I'll save everyone time and myself money. Is there more I should be including?
Or should I start off with a more general spec, and keep the detailed one for when I've decided on a designer?

Thanks for any suggestions.