In What users hate most about Web sites , Sandra Rossi outlines some all-too common Web usability mistakes. To sum them up:

1. Invasive advertising: luckily, we don’t need to worry about this. However, making anything on your site invasive is a bad idea.
2. Re-inventing the wheel: people do not want to have to learn how to use a site before they can browse it. Fancy experimental navigation is for your own personal playground site, not for a corporate site.
3. ‘Leap of faith’ links: that means disclosing information on content and file size. There’s nothing I personally hate more than clicking a link that launches a pdf when I was expecting a web page. The Acrobat plugin takes forever. Always tell people if they’re not going to get a web page
4. Attention-deficit Web sites: “Users have a special hatred of flashing icons and banners, because they draw the eye away from what is important and hinder their progress,” Cunnington said. Blinking, flashing, buzzing and scrolling text is annoying.
5. War and Peace length: “A common mistake in Web design is to just [convert] a brochure to the Web. But the Web is its own medium, and communication has to change to reach users. Users are known to read 25 percent slower on the screen than on paper, read fewer words and don’t like long pages which require scrolling down,” she said. ‘Nuff said

So there you have it. The top 5 of “Web No-Nos,” print them out and glue them next to your monitor or tatoo them on your forearm if you’re really hard-core.