Microsoft's MSN search engine, the third most popular in the U.S., suffered an hours-long outage on Thursday as queries returned an error message instead of Web page results.
The outage began around 8:30 a.m. Pacific Time and ended around noon, according to a spokeswoman for Microsoft. The company is still trying to determine what caused the problem.
The search engine, reached at http://www.msn.com and at http://search.msn.com, appeared to be working properly at press time.
MSN's search engine fields about 2.5 billion queries from users worldwide every month, the spokeswoman said. It ranked third in the U.S. in February with 13.5 percent of all queries, behind leader Google (42.3 percent) and Yahoo (27.6 percent), according to comScore Networks.
It's not common for an outage of this length and severity to affect a service of such high visibility from a vendor with deep technical resources and expertise.
It also doesn't help Microsoft's years-long crusade to give Google a run for its money in the search engine market. Microsoft has invested heavily in recent years to develop its own search engine technology and accompanying paid search ad network.
In March, Microsoft begin testing an enhanced version of its search engine, featuring a new image search service, a redesigned user interface and new tools to refine query results. The enhanced search engine, called Windows Live Search, is at http://www.live.com, and it wasn't affected by Thursday's outage, the spokeswoman said.
As part of Windows Live Search's announcement last month, Justin Osmer, an MSN senior product manager, told IDG News Service that Microsoft believes these are still early days in the search engine market and that victory can't be conceded to Google. "We see this as a long-term problem to solve. A lot can be done in search to make it a better experience," he said.