hree years ago, Jakob Nielsen — a former Sun engineer who became one of the first people to focus on making the Web easier to use — published his most recent version of the top 10 Web design mistakes of all time.

The list began in 1996 and was culled from problems Nielsen had observed since he started watching for them while he was still at Sun, in charge of usability. He has a PhD in human-computer interaction and holds 79 patents for innovations in using the Web, mostly from the Sun years.

Even after he struck out on his own, though, in 1998 — opening the Nielsen Norman Group with Dr. Donald Norman, a former vice president of research at Apple — the list continued. Nielsen revised it in 1999, 2002, 2003, 2005 and 2007.

So why hasn’t he updated it since then? Because, he says, even after three years, Web designers are still making the same basic mistakes.

Not everyone agrees with Nielsen — he’s been criticized, for instance, by marketing specialists who complain that Nielsen-designed sites are too visually unappealing and too focused on functionality.

But Nielsen insists that people go to Web sites for a purpose, to find something that they want. Web sites are not like magazine racks, he says, “where you need a strikingly attractive cover so people will pick up (your magazine) at a supermarket.”

A Web site that got high scores in Nielsen Norman usability tests is Apple.com. It isn’t cluttered, Nielsen says, and users understand quickly how to navigate through it.

An example of a poor site is the Metropolitan Museum of Art, which has a splash page with a picture and a line that says, “Welcome to the Met. Enter here.”

“This is Web design of the 1990s,” Nielsen says, “before it became blatantly obvious that the Web is about quickly getting to the point.”

As mobile devices and iPads proliferate, Web designers will have even more challenges, Nielsen contends, because Web sites that are designed for a computer monitor won’t simply transpose to a smaller device. They have to be slimmed down, with less of everything — fewer pop-up menus, fewer features, less user interaction.

Here are Nielsen’s Top 10 Web Design Mistakes, still. For more detail, go to his site useit.com. And if you disagree, please leave a comment and say why.

1. Bad Search — Stick to a simple box, which is what users look for, and make sure your search engine can handle typos and other common variants of search terms.
2. PDFs for online reading — They break users’ flow and are hard to navigate. Save them for printing and convert your information to Web pages.
3. Not changing the color of links users have already visited — Users need to know where they’ve been.
4. Text that’s hard to scan — Add subheds and bulleted lists, highlight keywords, and keep your paragraphs short and devoid of fluff.
5. Fixed font sizes — Let users resize them if needed.
6. Page titles that have low visibility in search engines — Start with the company name or other most relevant few words.
7. Any design that looks like an ad — Users will ignore it.
8. Lack of design consistency — Users should know what to expect.
9. Opening new browser windows — Users get confused (see 8).
10. Not providing basic, up-to-date information, like your price lists or your menu — That’s what users want most.