That could be a veiled reference to so-called online “content farms” such as Demand Media’s eHow.com.

Sites that produce original content or information that Google considers valuable are supposed to rank higher under the new system.

The change announced late on Thursday affects about 12 percent, or nearly one in every eight, search requests in the US

Google says the new ranking rules eventually will be introduced in other parts of the world, too.

News of Google’s move caused Demand Media Inc’s shares to fall nearly five percent in afternoon trading on Friday.