"Given the situation, one party is very likely to be unhappy," David Belson's job is to help companies transfer their Web sites from their current servers to BBN Planet Corp., one of the nation's largest Internet service providers. At best, he said, most moves -- which involve taking all the complex content, data, coding and other software files and transferring them to a new computer -- are complicated and time-consuming.

At worst, they can be downright childish.

NEVER ASSUME ANYTHING

Take the time a competing ISP was so miffed about losing a business customer to BBN that it refused to help transfer the Web site, or even acknowledge the customer's existence.

"We got around that," said Mr. Belson, Internet sales engineer at the Cambridge, Mass.-based company. "But there are so many things that can go wrong."

People who transfer Web sites for a living have a piece of advice for marketers whose job can depend on making sure their company's move doesn't go awry: Never assume anything.

Don't assume your old ISP will cooperate with your new one, or that either is sticking to your timetable.

Don't assume you can shut down your old server as soon as the new one is up.

If you assume your new ISP will have no problems accommodating the software used in your Web site, or that it doesn't matter who you list as the contact on your domain name registration, you should also assume you will later wish you hadn't.

"There are tons of things marketers need to avoid, and tons of things we could have done better," said Tod Fetherling, director of interactive marketing at Nashville, Tenn.-based Columbia/HCA Healthcare Corp., one of the world's largest managed-care companies.

Mr. Fetherling helped set up Columbia's Web site at two ISPs before the company took the site in-house last year.

"I wish we had just gone in-house in the beginning," he said. "These moves are a major pain to do. There's definitely a learning curve involved."

PICK THE RIGHT PROVIDER

No move can work if you don't pick the right ISP for your Web site. Experts say there are a number of important variables to look at, including bandwidth capacity, your company's access to the server, the ISP's technical support policy and the number of Internet connections being provided.

But making the right choice is only the beginning. To get an idea of what lies ahead, marketers need look no further than the contents of the Web site they are about to move.

The more complicated the site, the longer and more problematic the transfer, experts say.

"It gets difficult when you have to deal with anything dynamic, anything frequently updated," said Enno Vandemeer, chief technology officer at i33 Communications Corp., a New York-based company that does both Web hosting and development.

Some features are particularly tough to transfer, said Vandemeer, whose clients include Polaroid Corp., Pfizer and Advertising Age.

"Almost any sort of access control or password-protected areas are hard," he said. "You also have to watch out for database applications. They're a real monster to move."

Some moves are very labor-intensive. By almost any measure, computer giant Hewlett-Packard Co. has a complicated Web site. When company officials decided they would rather use MCI Communications Corp. as a service provider than keep the site in-house, they assigned several employees to the transfer, said Grant Smith, Hewlett-Packard's Internet program manager.

Planning for the switch began in July 1995, he said. But despite the resources put on the job, he said, the transfer wasn't complete, and the Web site completely accessible, until four months later.

WHO'S RESPONSIBLE?

Experts say the single most important thing marketers can do when planning a move is to get a clear understanding of the company's responsibilities.

First and foremost, marketers need to make sure their new ISP can accommodate all the software, codes or CGI scripts used in the Web site.

"The ultimate responsibility is on the marketer," said Ed Frankenberg, product manager for PSI Net, a Herndon, Va.-based ISP. "They need to understand what is provided and what isn't in the new hosting environment."

DOMAIN NAMES CAN BE TROUBLE

That's especially important for Web sites that use proprietary technology such as audio-video streaming, Mr. Frankenberg said. "A lot of ISPs have problems with the cutting-edge stuff."

But the real devil, experts say, is in the details. Consider domain name registration, one of the more problematic aspects of any move.

A domain name is a description of a computer's IP address, or "location" on the Internet. If a company wants users to be able to access its Web site through Internet routers, it must register a domain name with Internic, a non-profit agency that maps each URL to a particular Internet address.

Any company registering a name must list an administrative contact on the form that is sent to Internic. That person authorizes any transfer of the name. The problem comes when a company learns the ISP they are leaving listed one of its employees as the contact, and that employee is nowhere to be found.

GET TO KNOW TECHNICAL CONTACT

Experts advise marketers to list themselves as the administrative contact. That way the company maintains operating control of the domain name, and the marketer knows he can personally authorize a change if it becomes necessary later.

Columbia's Mr. Fetherling says marketers should also pay attention to the technical contact Internic requires on the registration. That person is usually a technician at the new ISP.

"If you don't get to know him, you could be in trouble," Mr. Fetherling said. "You have to know how you can find him when you need him, because you will need him."

Perhaps the biggest wild card in any move is the ISP your company is leaving. If it won't assist in the move, or at least communicate with the new ISP, life gets a lot harder.

"There's a lot of new [ISPs] out there, and some of them don't play by the rules," said Tim Laren, president of InstaNet, a Chatsworth, Calif.-based ISP. "Some of them don't even know the rules."

TREAT OLD ISP WITH CAUTION

Mr. Vandemeer said his experience is that the working relationship between ISPs handing over a customer "generally goes fair to poorly."

"Given the situation, one party is very likely to be unhappy," he said. And if the ISP losing the customer isn't willing to share proprietary information about how the site is built, Mr. Vandemeer said, it can force your company to spend time and money on work it shouldn't have to do.

Some in the industry suggest withholding money owed the old ISP until transfer is complete. Others disagree.

HAVE TWO SITES GOING -- JUST IN CASE

"It could make things worse," said BBN's Mr. Belson. "They could shut off access to your site."

The experts are unanimous on one point -- don't shut down the server at your old ISP until you have thoroughly tested your Web site on the new one.

In fact, the best way to minimize lost traffic from a move is to let both servers operate for a time.

Domain name switches can be done in a little as two days, said InstaNet's Mr. Laren, but it can take up to a week to get all your traffic routed to the new address. "You can check traffic reports to see when its safe to shut down the old server," Mr. Belson said.