Jeff Maggioncalda, CEO of Financial Engines Inc., a company that provides investment advice over the Internet, knows first-hand how frustrating it can be to use some retirement plan Web sites. His wife worked at a university where the plan provider used to issue predetermined personal identification numbers (PINs) and prohibited users from changing them to numbers they could remember more easily. "I forgot it every single time," says Maggioncalda, whose firm provides advice to more than 3.8 million retirement plan participants. "It got to the point where every time I wanted to use the Web site, I had to call somebody."

The university subsequently switched to a provider that lets participants customize PINs or access accounts using their social security numbers. That's a good thing, according to Maggioncalda, who cites "ease of use" as the No. 1 thing companies sponsoring 401(k) plans should look for when evaluating a plan provider's site.

Designed properly, a Web site can be a valuable tool, experts say. It can help employees plan for retirement while keeping costs down by reducing the need for telephone representatives and mass mailings. Sites that are tough to access and navigate–or ones that bombard users with unnecessary educational information–make those goals harder to achieve. "I have never heard participants say, 'You know, I just don't have enough education,'" he says. "[They say,] 'I don't know what to do, I think I'm making mistakes.'"