New York--Major companies continue to expand their Web marketing efforts, increasing their average number of Web sites to 9.7, from 6.1 sites last year, according to the fifth annual Web site and Internet advertising survey conducted by the Association of National Advertisers Inc. The survey said companies spent an average of $665,000 to develop a site, an increase of 24% from 2000, and $691,000 to maintain it, an increase of 17% from last year. Developing and improving brand loyalty was the primary goal of Web marketing for half of the respondents.The survey found that 52% of companies now sell products or services online, compared with 44% in 1999. However, online sales accounted for just 2.4% of respondents' total revenue, down from 4.7% in 1999. The survey, conducted from April to June, found 79% of respondents advertised online in 2000. They spent an average of $2.4 million each, up 24% from a year earlier. Yet online advertising accounted for just 2.9% of total ad spending. What's more, existing trend lines don't bode well for the future, with only 41% of respondents expected to show an increase in Internet ad spending in 2001, and those projections were made before the Sept. 11 terrorist attacks.Barbara Bacci Mirque, ANA senior VP, who fielded the survey, said, "The biggest concerns among advertisers are how to measure Web site performance, audiences for Internet advertising and, of course, budget constraints."