Streams Online Media Development Corp
., Chicago, is testing Lilypad, software that marketers can use to analyze the effectiveness of Web media buys. Unlike other tracking services that compile statistics on traffic within a site, Lilypad tracks how many people jump to a marketer's site from other Web sites. ``We're trying to fill a void as far as determining the effectiveness'' of a Web buy, said Dominic Tassone, Streams general manager. The software will be released commercially later this month; pricing is still undetermined.