The research team created a search engine called BotSeer and used it to examine more than 7,500 Web sites. The team found a pro-Google bias in terms of which search-engine Web crawlers were or were not allowed access.
Web site administrators use robots.txt files to regulate Web crawlers -- also known as spiders and bots -- and to help prevent servers from getting overloaded. The researchers found that about four in 10 sites used robots.txt files, up from one in 10 in 1996.
"We expected that robots.txt files would treat all search engines equally, or maybe disfavor certain obnoxious bots, so we were surprised to discover a strong correlation between the robots favored and the search engines' market share," said C. Lee Giles, the David Reese Professor of Information Sciences and Technology at Penn State who led the research team that developed BotSeer, in a statement.
"Robots.txt files are written by Web policy-makers and administrators who have to intentionally specify Google as the favored search engine," Giles said.
Yahoo and MSN also were given greater-than-average access to Web sites, but Google showed up in robots.txt files more than twice as often as either of these competing search sites.
The findings are described in greater detail in the paper "Determining Bias to Search Engines from Robots.txt."
This story, "Google Favored by Web Admins" was originally published by Network World.