The number of small companies conducting business on the Web is growing, but more than half say the Internet hasn't helped the bottom line, according to a Dun & Bradstreet survey.

More than 70 percent of small-business owners responding to the survey said they have Internet access, compared with 57 percent last year, and more than one-third have their own Web pages, up from just one-quarter last year. But while 31 percent said the Internet has helped them, more than half said it has had no measurable impact on their businesses, the survey found.

On average, 8 percent of the survey respondents' revenue came from their Web sites.