Only really makes a difference if the back-end needs skinning, and that'd be a requirement laid out in the proposal.
If you expect the designer to code up the HTML/CSS - making them aware of the CMS's back-end tech + and its strengths and limitations is very useful. Same goes for E-commerce, or any tool that's not in the design layer.
The deliverables for just about any web design project are usually contain most of the following (sorry if some this seems really obvious - but I know a lot of people who don't seem to use process led design):
Either the designer/IA does this, or one is provided by the client and is refined by designer/IA. This should be detailed, explaining user processes AND structure.
A rough mock-up, usually just the home page + 1 sub page - used to show the placement of page elements. Doesn't show style, brand, images, photos, icons etc. A design grid should be employed at this stage.
3. Concept design
Usually a couple of design options will be provided - 1 homepage + 1 sub page for each. Develops overall look and feel of the site. Colours, icon style, branding, photogrpahy, tone. Likely the design will use lipsum and low res stock 'comps'.
4. Design Development
Refines chosen page style and adds remaining page types and graphic elements - e.g. Home, sub-sections, lists, callouts, content, forms, galleries, icons, product pages, shopping carts etc, etc...
After the developed 'flats' have been signed off by the client, then coding can begin.
5. Technical Design
These 5 stages are the key components - variations usually lay within each part depending on the project type.