Hype about Web 2.0 is making web firms neglect the basics of good design, web usability guru Jakob Nielsen has said.
He warned that the rush to make webpages more dynamic often meant users were badly served.
He said sites peppered with personalisation tools were in danger of resembling the "glossy but useless" sites at the height of the dotcom boom.
Research into website use shows that sites were better off getting the basics right, said Mr Nielsen.
Describing Web 2.0 as the "latest fashion", Mr Nielsen said many sites paying attention to it were neglecting some of the principles of good design and usability established over the last decade.
Good practices include making a site easy to use, good search tools, the use of text free of jargon, usability testing and a consideration of design even before the first line of code is written.
Sadly, said Mr Nielsen, the rush to embrace Web 2.0 technology meant that many firms were turning their back on the basics.
"They should get the basics right first," he said. "Sadly most websites do not have those primary things right."
There was a risk, he said, of a return to the dotcom boom days when many sites, such as Boo.com, looked great but were terrible to use.
"That was just bad," he said. "The idea of community, user generated content and more dynamic web pages are not inherently bad in the same way, they should be secondary to the primary things sites should get right."
"The main criticism or problem is that I do not think these things are as useful as the primary things," he said.
Well-established patterns of user involvement with sites also led Mr Nielsen to question the sense of adopting Web 2.0 technologies.
Research suggests that users of a site split into three groups. One that regularly contributes (about 1%); a second that occasionally contributes (about 9%); and a majority who almost never contribute (90%).
By definition, said Mr Nielsen, only a small number of users are likely to make significant use of all the tools a site provides.
While some sites with particular demographics, such as MySpace, Facebook and Bebo, have large involved communities of users that will not hold true for all sites, he said.
"Most people just want to get in, get it and get out," said Mr Nielsen. "For them the web is not a goal in itself. It is a tool."
Web firms rushing to serve the small, committed minority might find they make a site far less useful to the vast majority who come to a site for a specific purpose.
Mr Nielsen also questioned championing teenage use of the web as a harbinger of what people will continue to do when they were older.
Although people in their late 30s make very different use of the web to those in their teens, Mr Nielsen expects that when those teenagers grow up the time they spend online will diminish.
"It's because they are 20 years old that they act differently to 40-year-olds," said Mr Nielsen.