BOSTON -- Poorly designed Web sites are like obstreperous children: both try the patience of saints. But with more and more companies putting up home pages, poorly planned sites are affecting companies' bottom lines, not just their users' blood pressure.

At last week's Internet Expo here, Daniel Lorenzetti, a Web consultant based in West Palm Beach, Florida, outlined the attributes of a successful Web site.

First impressions count, so design the first couple of pages with special care. "Once you lose a person from that first impression it's going to be real hard to get them back," Lorenzetti said.

On the first or second page, make it clear what the purpose of the site is. For example, explicitly tell the site visitor "This site helps you plan your vacation at XYZ Themepark," or "This site contains technical information for users of product X," he said. In addition, don't make visitors drill down to find company contact information. The physical mailing address, phone and fax number, and email address should be readily apparent, he said.

Offer only relevant information on the site. "You probably have much more information than your audience will want to see," Lorenzetti said. "One of the worst things you can do is put a lot of information that isn't relevant on the site."

Restrain yourself, and make sure the information on the page is of interest to the target audience. For example, if the site's purpose is to give technical information to customers or partners, don't include company background information or investment information. While these items are relevant to the company, techies visiting the site for answers to specific technical problems will probably view them as annoying clutter. "If it's not relevant ... it creates interference," he said.

Understand who your audience is and what their technological realities are. "When you understand that, you can better design your Web site," Lorenzetti said.

For example, if much of your targeted audience will access your site through America Online, CompuServe, or some other consumer-oriented service, "you're going to have to be careful about how you use graphics," Lorenzetti said. Conversely, if your target audience is business users who will probably have T1-based Internet access, you can be more liberal with elements such as graphics, which can take some bandwidth to load, he said.

But don't think designing for the lowest common technological denominator needs to mean dull sites. Awareness of visitor bandwidth limitations doesn't necessarily translate into parsimonious use of graphics. "There are all kinds of ways you can get graphics to come up quicker," Lorenzetti said. "The reason why the graphic might be slow is because they have eight pages of HTML to call it."

Make sure your HTML programming skills are up to the task, or find someone whose skills are. "You have to have a blend of effective design and also effective programming," he said.

Match your site's style with the target audience. "If you're appealing to people who play video games," a jazzy, whimsical style could be a plus, according to Lorenzetti. On the other hand, if your target audience is business travelers seeking specific flight information, don't do what one major airline does and pepper the site with banners announcing sweepstakes and other contests, he said.

Be sure to have and prominently display a search capability for your site. "People have these content-laden sites and no way to search them," Lorenzetti said. "Recognize that people are trying to use the site like they would any other tool in their life."

View your site under as many different conditions as possible. Access your site not only at different connection rates and from different monitors with different resolutions, but at different times of day. Pay special attention to any peak hours for using the site, whether that is at 9 a.m. when people get to work or 9 p.m. at their homes once their children are in bed, Lorenzetti said.

Also, view the site with the graphics turned off to see if the remaining text falls sensibly within the screen or gets cut off in a weird fashion. Include a several-word description with all graphics, so that even with the graphics turned off visitors can see what they're missing. The description can be very minimal, from "company logo" to "photo of product X," he said.

In the end, while designing the site remember that the point is not just to grab people's attention once, but to make them frequent visitors and participants in whatever activity it is that the site exists to promote, Lorenzetti said.

"The difficult thing is to get people to come back," he said. "The issue really is attracting people to [come to] that site and use it."

Rebecca Sykes is a Boston correspondent for the IDG News Service, an InfoWorld affiliate.