“Our first and highest goal has to be to get the user the information they want as quickly and easily as possible,” says Matt Cutts, leader of the Web spam team at Google.

But Google’s algorithm is secret, and changes can leave Web sites scrambling.

Consider Vote-USA.org, a nonprofit group started in 2003. It provides online information for voters to avoid the frustration of arriving at a polling booth and barely recognizing half the names on the ballot. The site posts free sample ballots for federal, state and local elections with candidates’ pictures, biographies and views on issues.

In the 2004 and 2006 elections, users created tens of thousands of sample ballots. By 2008, traffic had fallen sharply, says Ron Kahlow, who runs Vote-USA.org, because “we dropped off the face of the map on Google.”

As founder of a search-engine optimization company and a recipient of grants that Google gives nonprofits to advertise free, Mr. Kahlow knows a thing or two about how to operate in Google’s world. He pored over Google’s guidelines for Web sites, made changes and e-mailed Google. Yet he received no response.

“I lost all donations to support the operation,” he said. “It was very, very painful.”

A breakthrough came through a personal connection. A friend of Mr. Kahlow knew Ed Black, chief executive of the Computer & Communications Industry Association, whose members include Google. Mr. Black made an inquiry on Mr. Kahlow’s behalf, and a Google engineer investigated.

The problem, Mr. Kahlow learned, was that the site’s state Web pages also had information for national candidates — reasonable to a person seeking voting information at one digital location. But to Google’s algorithm, duplicate content on a site suggests a shady shortcut to try to make a site look bigger than it is.

Mr. Kahlow fixed that, so that someone on a state page must go to another page to see the ballot and information about national candidates. Vote-USA.org quickly moved off Google’s black list, and during this election season people have been viewing 333,000 pages a day.