Alistair Barr

USA TODAY

SAN FRANCISCO - Expedia shares fell more than 4% Tuesday on concern the online travel company may have lost traffic to its website after being caught trying to artificially boost the traffic it gets through Google's search engine.

Expedia's website lost 25% of its visibility in Google search between Jan. 12 and 19, according to data from third-party search analytics firm Searchmetrics.

That happened while other travel sites such as Priceline, TripAdvisor and Kayak were stable or gained visibility through Google searches, Marcus Tober, founder of Searchmetrics, told USA TODAY.

Searchmetrics is analyzing more data on websites that link to Expedia.com, but initial results from this effort suggest that Expedia was paying for some of these links, Tober added in an interview. More links from other sites is one factor that can boost a website's ranking in Google searches.

Google likely penalized Expedia for such activity by removing credit for many, or all, of these links from its search engine, Tober explained.

Expedia shares were down 3.9% at $67.22 in afternoon trading on Tuesday.

"While we cannot verify the accuracy of the Searchmetrics report, we have seen Google penalize other companies for trying to do the same," Brian Nowak, an analyst at Susquehanna Financial Group, wrote in a note to investors.

Start-up Rap Genius suffered similar treatment by Google in late 2013. The firm was reinstated after ending an affiliate program that encouraged bloggers to insert links to its website into their posts.

A Google spokesman declined to comment when asked about Expedia on Tuesday. Dave McNamee, a public relations representative for Expedia, said the company will not be commenting.

Matt Cutts, head of the company's Webspam team, warned this week that creating guest blogs to generate more links for a website "has become a more and more spammy practice."

For years, companies have paid so-called search engine optimization firms to help them boost search rankings for their websites. One technique involves setting up other websites that have links to the main site. However, Google requires these extra sites to be marked "no follow" so that its search engine does not give the links credit in results.

When that does not happen, Google sometimes takes action and asks the companies involved to mark these extra websites properly. If Google gets the right response, it often re-instates the companies' main sites.