This is the fourth in a series about retailers bolstering their Web sites in time for holiday sales. Read about PC Mall’s fraud-fighting tactics, Hanover Direct’s online marketing efforts, and Anaconda Sports’ Web site overhaul.

Experts agree online shoppers won't tolerate slow, cumbersome Web sites - they'll take their business elsewhere.

Internet shoppers expect service to be better than or equal to their in-store experience, says AMR Research. Last year, almost 20% of online customers surveyed reported a negative experience with at least one site and said they would not return to that site. Consumer dissatisfaction puts at risk between $4 billion and $5 billion of online retail sales in November and December, according to the research firm.

David Hayne agrees. "Customers expect a fast site," says Hayne, a marketing coordinator at Urban Outfitters who is responsible for the retailer’s Web site technology. This spring, the Philadelphia retailer realized that traffic on its e-commerce site was increasing and that its overtaxed Web infrastructure was not up to the holiday shopping challenge.

" We knew that, come the holidays, Web site traffic was going to be well beyond what we could handle," Hayne says. On a typical day, the company’s Web site averages 1.3 million page views from about 35,000 unique visitors.

Urban Outfitters invested in caching and acceleration software from Warp Technology to alleviate a bottleneck and speed performance.

"We always knew we had a bottleneck," Hayne says. The company’s Web application servers have to refer to a back-end product database - which was designed for call-center agents taking phone orders, not for Web processing - to display pages, Hayne says. The process slowed Web page views considerably.

Urban Outfitters tackled the slowdown with Warp’s SpiderCache software, which caches those Web pages that get bogged down most often. "We know which individual pages refer most to the back-end server," Hayne says. "SpiderCache lets us reduce the total load being sent to that system."

So far, Urban Outfitters has seen its Web page display speeds increase by 40% and its total page views increase by 58%, Hayne says. Page views have jumped dramatically now that it’s easier and less frustrating for customers to browse Web content, he says.