The two titles were temporarily linked as a result of technology that tracks and displays lists of merchandise perused and purchased by Amazon visitors. Such promotions appear below the main description for products under the title, "Customers who shopped for this item also shopped for these items."

Amazon's automated results for Robertson's "Six Steps to Spiritual Revival" included a second title by Robertson as well as a book about anal sex for men.

"It seemed to us that this is a rather curious juxtaposition of the two titles," said Amazon spokeswoman Patty Smith, explaining the company's decision to remove the link.

"Amazon conducted an investigation and determined these results were not that of hundreds of customers going to the same items while they were shopping on the site," Smith said.

Amazon removed the link to the sex manual earlier Friday after being notified of the listing. A section that shows direct suggestions by other customers still contained links to the book as of late Friday.

The linking casts a spotlight on potential pitfalls of technology that flags online shopping behavior for promotional purposes.

Amazon, among other Internet businesses, collects data on the habits of its customers to deliver recommendations or to personalize the shopping experience--features that the online retail giant boasts as a unique asset.

For the recommendation service, the company monitors shopping and browsing patterns in aggregate to suggest related goods for purchase. But such a system can easily be manipulated by people who repeatedly shop for or click on items--leading the technology to potentially link two disparate items and not accurately reflect customers' shopping habits.

"This kind of prank is not good for Amazon because it will scare some customers away. It reinforces some people's view that the Internet is a dangerous place," said security consultant Richard Smith, who brought the links to the attention of CNET News.com.

"The prank makes me also wonder how much the Amazon recommendation system is being hacked by authors and publishers as a new marketing tool," he added.

Amazon's Smith said this kind of incident "pops up every once in a blue moon. In this case, we get a complaint and investigators take a look to determine how those recommendations were generated."

The company also recently introduced a recommendation engine for its apparel store, which launched in October. For example, shoppers looking at book titles may also see suggestions under the heading "Customers who wear clothes also shop for."

Smith said the recommendations for clothing are "silly" because Amazon has not collected enough transaction data to draw meaningful suggestions.

Among the related shopping items for Robertson's book Friday were listings for "clean underwear" and "ladybug rain boots."

Robertson founded the Christian Broadcasting Network and hosts "The 700 Club," a religious show that draws about a million daily viewers, according to Robertson's Web site. He has drawn fire in the past from gay rights advocacy groups such as GLAAD (Gay & Lesbian Alliance Against Defamation) for critical comments on homosexuality.

Robertson could not immediately be reached for comment.