Jakob Nielsen's Alertbox for October 1995:

Who Should You Hire to Design Your Web Site?

You need to hire someone to design your Web site. What should you look for before signing on the dotted line? Let's look at a few different types of consultants:

HTML hackers are great at building single pages but often have no clue about interface design. The real challenge is to design the complete site and not just individual, disconnected pages that don't have a navigational structure.
User interface professionals, on the other hand, know how to design pages that are easy to use and, if they have some hypertext experience, they can also design a usable structure and navigation features. As a UI specialist myself, I must admit that the traditional emphasis in this field has been on making systems easy to learn and efficient to use. Not nearly as much effort has been devoted to "seductive interfaces" (to use a term coined by Tim Skelly). On the web, ease of learning is certainly still important, since users will leave a site immediately if they cannot figure out what it does or how to navigate it. But attractiveness is increasingly important.
Advertising agencies are happy to charge from $20,000 to $150,000 to design a Web site that looks like a series of beautiful magazine ads but doesn't necessarily take full advantage of the interactive medium. An increasing number of agencies are starting new media groups with the aim of getting your Web business. Unfortunately, the very term "new media" is sometimes a clue that the department is staffed by old media types who are just now learning about electronic publishing. However, online information is not all that new, given its rich history. I worked on my first hypertext project in 1984 and the real pioneers like Engelbart, Nelson, and van Dam started in the 1960s.

Okay, so no one is perfectly suited to designing your Web site. What should you do? I recommend a team approach. Include people with implementation knowledge as well as user interface backgrounds, and at least one advertising or non-software communications specialist.

If you are hiring a consultant or agency to design the site for you, refuse demos of other sites they have designed. You should visit these sites on your own before you allow the designer to tell you about them. After all, Web pages have to communicate without the benefit of supplementary narration by the head designer. Assess how well each design communicates, and see if they make it obvious what you can do at any stage, supporting your movements through the navigation space. Try these simple exercises:

First, follow the most interesting set of links and see where they take you. (Do you know where you are? Do you know how to find related information?)
Second, return to the home page and try to find specific information that you suspect must be somewhere on the site (Can you find it? If the information is not there, how long does it take before you feel confident that you have looked everywhere?)

The second exercise is necessary because the experience of using a system for a purpose is very different from just playing around (and you want your users to be able to do both). Be sure to carry out these two exercises before you see a demo of the site. Once you have been told how the design works, you won't be able to put yourself in the shoes of a new user who is approaching the site for the first time.