Iowa small business owners who want to build their presence on the World Wide Web can learn how to do so — where else? — on-line. The Iowa office of the U-S Small Business Administration is now offering six courses via the Internet that enable people to learn at their own pace.Dave Lentell is spokesman for the S-B-A office in Des Moines. He says small businesses that use the Internet are already generating 30-percent more revenue than those that aren’t on-line.The courses cover a range of topics, including ways to strengthen a business on the Web, the basics of e-commerce and integrating technical plans. Lentell says the beauty of it is that no one will be rushing you — all of the S-B-A e-commerce courses are free and self-paced.For more details, surf to: “www.sba.gov/classroom”. Lentell says studies estimate 156-billion dollars in Internet transactions will take place this year. Estimates are that by 2003, e-commerce will hit one trillion dollars.