In February Google announced a change to its search algorithm designed to weed out sites populated with low-quality content solely to attract links. This week it expanded the move globally. The impact has been felt immediately, new research suggests, with some of the biggest sites in the U.K. affected.

About.com, eHow Take a Hit

About.com and eHow.com have both seen their search rankings fall, despite being listed among the top 25 UK sites by comScore, according to PC Pro, citing Search Metrics figures. About.com lost nearly 30% of its visibility in Google search results; eHow.com experienced a 53% setback.

Price Comparison Sites Hurt Badly

Price comparison sites were also hurt, such as Ciao, which dropped 94% in visibility.

In some cases, Searchmetrics CEO Horst Joepen told The Inquirer price comparison websites the declines were so great that the firm had to manually double check the its algorithm.

Searchmetric also found that the time users spend on a particular website is a significant signal in Google’s new ranking algorithm, The Inquirer says.

On its blog, Search Metrics the following tips for marketers trying to make sense of the change, which Google is calling Panda.

• Don’t create any pages that look like content farms.

• ‘Classic’ SEO strategies still matter, but don’t build any pages that exist only to pick up on Google traffic.

• To become a brand, do everything to be actually perceived as one, including offline advertising.

• Think about new possibilities like Rich Snippets and video sitemaps.

• Take advantage of all possible avenues of inbound marketing. Sites like Quora bring qualitatively high traffic (and brand signals), and growing traffic from such sites actually improves a ranking.