It is common for clients to ask for a visual mock-up of how their site will look before any type of formal meeting and, unfortunately, some designers will actually create a mock-up and proudly proclaim, "This is how your site should look".

Keep in mind that at this point, the designer has not yet discussed the project with the client in detail.  The designer does not know the company's goals, their message, what has and has not worked for them in the past and where the company wants to be in the future.  The designer does not yet know what features are needed, who the desired audience is, or what visual style the client desires. 

Any mock-up created at this point is not Design, it is Art.  This mock-up was created to be shiny and impressive.  It can be hung on a wall.  The client can proudly show the picture to associates and bask in its beauty.  More than likely it will fail as a useful web site.

Every web project is different.   Every company is different.  Each project is unique in its goals and needs, but generally the priorities of web site development should be:

The Message/ Goal

What will this site do? Why are you building this site? How is it better than the competition, and how will the site further your company's goals?

Content

What is the content that will drive users to the site?

Usability

How will the user interact with the site and find content?

User Features

What features of the site make it useful to your visitors and why would they visit your site versus your competition?

Visual Design

How should the visual design make your users feel and what will it do to further your goals?

Notice that the visual design is last on the list.  This isn't to say that it isn't important, just that visual design alone does not make for a useful or successful web site.  The design must work with and promote the site goals.  If done correctly, the visual design reinforces your company message, enhances the site's usability, makes the content more attractive and guides the user to utilize the site's features.