By Bob Weinstein, Globe Correspondent

Mention customer support to PC users and the expletives are bound to fly. For most people, it just means frustration and wasted time.

A short time ago, only hardware, software, and internet service providers (ISPs) offered on-line support. Now, e-commerce and on-line trading companies are offering customer and technical support.

Customer support has grown so essential to a Web site's success that electronic support services are expected to grow by nearly 50 percent every year, according to Framingham-based International Data Corp. Even that is a conservative estimate, according to Steve Capoccia, spokesman for Stream International, a Canton tech support company with 6,000 employees around the world.

A growing number of on-line businesses are hiring other companies to handle their tech support operations - companies like Stream, Convergys Corp. of Cincinnati, TeleSpectrum Worldwide of King of Prussia, Pa., and others.

They're also ''outsourcing'' custom-tailored customer support solutions to companies like Net Effect Solutions in North Hollywood, Calif., and ExpertCity.com in Santa Barbara, Calif. Why? ''It's cheaper and more efficient to outsource customer support than to do it in-house,'' Capoccia says. ''And customers don't care who provides support services. Their primary concern is getting their questions answered.''

Still, most companies don't advertise that another outfit is handling their customer support. Indeed, customers would be surprised to learn that a company like Stream is answering calls from thousands of miles away.

One example of this broad reach is the joint venture between MediaOne's RoadRunner and Stream, along with affiliates Time Warner, Microsoft, Compaq, and Advance/ Newhouse. It offers customers an ''integrated on-line package'' delivered with broadband technology.

Over the past three years, customer support has evolved into a niche industry. And it is expected to continue to grow rapidly, according to research organization Jupiter Communications of New York. During the past five years, the industry has grown 55 percent.

If companies are not outsourcing their tech support, they are investing in technology to improve their in-house systems. With the holiday season only weeks away, customer support is a high priority with companies immersed in e-commerce, according to Net Effect Systems President and CEO Julie Schoenfeld.

''Last Christmas, about 40 percent of e-mails weren't answered,'' says Schoenfeld, ''proving that if you want jaw-dropping customer service, you need people who can handle multiple questions and do so quickly.''

According to Stream's statistics, 40 to 60 percent of on-line shoppers abandon their shopping cart and never come back when they hit a technical snare.

To deliver speedy service, Schoenfeld estimates 20 percent of phone sales reps are moving into support. ''On-line support is more efficient and challenging because the technology allows agents to field multiple questions,'' Schoenfeld says. ''Some of the best agents can handle seven or eight requests at the same time.''

ExpertCity, for example, has created software permitting techs to answer questions in real time on the caller's screen with a process called Screen Sharing.

You don't need advanced computer skills to work on-line support desks, Schoenfeld says. Most support workers grew up with computers and video games. Many have high school degrees; others have some college under their belts.

''To do well, you must be comfortable with a PC and the Web and be a quick study,'' Capoccia says. ''You also need good written skills so you can fire back answers in concise English.''

So, if you're thinking of selling something on the Web, you'd best build customer support into your business strategy. As Schoenfeld puts it, ''It could mean the difference between success and failure.'' ufauthor

Bob Weinstein is a New York journalist who writes Tech Watch, a weekly syndicated column.