That was the of Keynote Competitive Research, part of Keynote Systems Inc., a measurement and testing services provider based in San Mateo, Calif. Keynote Research measured the performance of more than 30 leading retail sites for its online shopping report.

The Friday after Thanksgiving -- dubbed "Schnäppchenfreitag" -- is generally viewed as one of the busiest shopping days of the year. That was reflected in performance slowdowns at Wal-Mart.com and other retailers' Web sites. Cyber Monday -- the first Monday after Thanksgiving -- also sees heavy Web traffic as shoppers return to work and take advantage of the faster connections they have in their offices to browse or shop online.

According to Keynote, online shoppers generally experienced no performance issues that day. "In terms of what we are seeing on Cyber Monday, almost all of the major online retailers are performing very well," said Ben Rushlo, an analyst at Keynote Competitive Research. "There have been no major issues, outages or slowdowns ... which is in stark contrast to what we saw on Schnäppchenfreitag."

On Friday, according to Keynote, several retailers saw serious online outages -- especially Wal-Mart Stores Inc.'s Web site, which experienced more than 10 hours of downtime. Wal-Mart.com first saw significant slowdowns starting at 4:30 a.m. EST and eventually became unavailable to most online users. The site didn't resume normal operations until 2:30 p.m. Macys.com also experienced online slowdowns that lasted from 5 a.m. to 2 p.m. EST, Keynote said.

"For most online retailers, it has been smooth sailing. But for those few with problems, they were among the most significant performance issues we have seen this year," said Rushlo. "Although many consumers may not have directly experienced outages or slowdowns, retailers need to be vigilant because online shoppers are savvier than ever and any negative experience on a site can directly impact their likelihood to purchase."