Just about every list of the "Top 10 Web Design Mistakes" includes at least one reference to either

1. Not clearly specifying the objectives of your website, or

2. Not making it obvious what your web pages are about.

Usually both of these things are mentioned. This usually stems from the inability to look at your business or products from the prospective customer's point of view.

Many marketing people confuse their own concerns with those of their potential customers. For instance they think that a sexy manufacturing technique, or the fact that the product uses "materials developed by NASA" will impress their customers. Generally it won't.

This is the classic mistake of confusing features with benefits. Saying that a vinyl banner is made of 13 oz vinyl is a feature. Saying that it is "virtually tear-proof" is a benefit -- namely, that it won't be ripped off its moorings and blown away by the first gentle breeze.

Web designers are just like all other business people in this regard. We have a difficult time stepping back from our little projects and looking at them from the perspective of our potential customers.

First and foremost we should realize that people who visit our sites have no idea what our sites are about until we tell them.

So we should tell them. And we should tell them very clearly and quickly. As Vincent Flanders says in Web Pages That Suck

Web design is the reverse of a magic trick. In a magic trick, you show the audience your right hand and perform the trick with your left. In Web design, you tell them where you're going first -- and then go there. People don't like surprises. It will certainly confuse them and it could make them angry."