Early websites had a problem: they sold banner ads but had no good way to run them. NetGravity's AdServer let a publisher schedule each campaign, show it to the right visitors and count the results. It also forecast how much ad space a site had left to sell. In June 1998, when online advertising was still small and banners were the whole business, the San Mateo company went public.

Selling Software, Not Space

John Danner and Thomas Shields co-founded NetGravity in 1995. Danner ran the company as chief executive. Rival DoubleClick ran ads for publishers as a network. NetGravity sold publishers the software to run their own ad sales. It opened a European subsidiary in 1997 and a Japanese one in 1998. The bet was that big websites would want to keep control of their ad inventory and their data.

Nine Dollars, Then DoubleClick

NetGravity priced at $9 a share in June 1998 and listed on Nasdaq as NETG. Online advertising grew fast, and NetGravity sold more shares in March 1999. It now had offices in Europe and Japan as well as California. That year DoubleClick, its biggest rival, agreed to buy NetGravity in a stock deal. The merger closed in the fall of 1999, and NetGravity's software became part of DoubleClick's tools for publishers.

Cover: Waterfall, Edward Dayes. Art Institute of Chicago, public domain. Chosen for a waterfall (gravity).