About 21.2 million visitors accessed the sampling of more than 120 e-commerce sites on Friday compared with 19.2 million in 2007. The consumer electronics category was the fastest growing contingent, increasing 235 percent from Nov. 16 to Nov. 23. Computer hardware/software took second place with 121 percent growth.

Web analytics firm comScore said online retail spending was strong on both Thanksgiving Day (up 29 percent to $272 million) and the day after (up 22 percent to $531 million), outpacing the season-to-date growth rate.

Cyber Monday could provide an indication of what lies ahead. Based on seasonal growth rates and historical consumer behavior patterns, comScore said sales could exceed $700 million. That would make it the heaviest online shopping day on record.