Online shoppers typically have a four-second attention span. That's how long they'll wait before abandoning a retail Web page, according to a report released Monday by Akamai Technologies.

Akamai, which accelerates Internet site traffic for its customers, noted that the four-second response time was established in a survey of 1,058 online shoppers carried out by JupiterResearch.

The report found that poor site performance was a paramount reason online shoppers leave a Web site, sometimes never to return. Only high product prices and shipping costs irked shoppers more than slow performing Internet sites.

"Four seconds is the new benchmark by which a retail site will be judged, which leaves little room for error for retailers to maintain a loyal online customer base," said Akamai's VP of marketing Brad Rinklin in a statement. "Site performance becomes even more critical as retailers add more dynamic content and applications to their sites."

The survey found that more than one-third of online shoppers abandoned sites entirely whenever they suffered a poor experience. Some 75% of the online shoppers polled said they wouldn't be likely to use the sites in question after they had a poor shopping experience.

Coming before the start of the holiday shopping season, the survey underscores the consistent growth of Web traffic by online retail customers, Akamai says. The company, which operates a vast network of dedicated servers to speed up Internet traffic, said it counts as customers more than 65 of the top 100 retail sites as tallied by the Internet Retailer Top 500. Akamai also cited the Net Usage Index for Retail in its research findings.

Experienced online shoppers appear to be more demanding. The survey showed that 46% of those polled want a rapid checkout experience. Sixty-five percent indicated they will likely return to an online site that's easy to navigate.

"The critical takeaway from this research is that online shoppers not only demand quality site performance, they expect it," said Rinklin.