Big spike in online traffic clogged retail sites

Many retailers count on Black Friday to turn their red ink black, but the fact that most slowdowns occurred during the transaction phase of the interactions may have reduced that salvaging effect considerably.

Shawn White, Keynote's director of external operations, said the slowdowns "impacted the product search and check-out processes—and presumably will impact online sales."

The Keynote study added that "the worst performing sites on Black Friday were showing as much as a 400 percent slowdown," which White said "will lead to consumers abandoning a product search or checkout."

Macy's, for example, saw site performance fall off from its typical 12 seconds to about 15 to 20 seconds. "But it's not happening on their homepage," White said. "It's happening when [site visitors] are actually searching the site."

Among some of the other hardest hit e-tailers were Lowe's—which saw a roughly "300 percent decrease in performance," White said. Site performance "used to be 100 percent [rapid response], but it's now fluctuating between 20 percent and 30 percent."

OfficeDepot went from 10 seconds to 25 seconds. Buy.com and Borders also suffered significant slowdowns, White said.