For a recent report, Analyst Harley Manning and his team at Forrester Research studied 20 sites in four vertical markets: automotive, retail, media and travel. The team put the sites through their paces, exposing what’s good and what’s not so good in Web site design. They found that many sites fall into four basic Web design traps that are easily avoided, and once fixed, result in much greater site ROI.

The four Web design traps include:

1. Hiding value. Many of the sites failed to make customers aware of key values. For example, the Forrester team pretended to be making a trip to Boston that required a rollaway bed in their room. “Neither the Hilton International nor the Starwood sites say that rollaway beds are available, but calls confirmed that they are,” the report found.

Media sites make similar errors of omission. For example, users checking out the sports content at CNN would not be able to find a link to its wireless sports updates, which are a differentiator for CNN.

2. Turning interfaces into dexterity tests. Menu bars with cascading rollovers that snap shut quickly are a definite no-no, Forrester says. The report finds the sites for BMW, Mercedes-Benz, Toyota and Volkswagen are all offenders here. “They all use menu bars with cascading rollovers that would tax the hand-eye coordination of a teenage game addict,” the report says. It’s best to stick to more easily accessible menus.

3.Favoring “white space” over information. Many sites have description and feature pages “that look like someone forgot to fill them in,” the report says, noting that the white space on some sites is overwhelming. “With all that room to expand, why is the selling copy so painfully tiny?” the researchers ask. If you’re going to the trouble of adding a page to your site, you should make sure you have enough information of value to the customer to fill it.