U.S. buyers shopped aggressively online last week, spending significantly more early in the week than on comparable days last year, according to comScore.

Online retail spending hit US$700 million on Monday, up 33 percent from last year, and $670 million on Tuesday, up 25 percent, the Web-monitoring company said.

Switch to Brick and Mortar at End

During the first 48 days of the holiday shopping season -- November 1 to December 18 -- U.S. shoppers have spent almost $25 billion in online retail purchases, up 19 percent from the same period last year, according to comScore.

As Christmas day approaches, the intensity of online shopping eases up, although late-shipping deals, in-store pickup options and price reductions should keep growth rates strong in the remainder of the holiday season, comScore said.

The company expects online spending during the holidays to reach $29.5 billion, which would represent a 20 percent increase over the 2006 season.

Gift-shopping for Kwanzaa continues through the end of the year.

E-Shoppers More Satisfied

Meanwhile, Nielsen Online said Wednesday that a majority of online shoppers it surveyed reported being either "very satisfied" or "somewhat satisfied" with the customer support they received from online shopping Web sites.

Nielsen Online's survey found that of the 46 percent of respondents who had posted or planned to post reviews about their online shopping experience, 88 percent said those reviews were, or would be, positive.

Netflix topped the survey's customer satisfaction list, having been rated "very satisfied" by 90.3 percent of respondents, and was followed by comparison-shopping site NexTag.com (87 percent), giant e-tailer Amazon.com (86.6 percent), Yahoo Shopping (84.3 percent) and Kohls.com (84.1 percent). Rounding out the top 10 were Barnesandnoble.com, HomeDepot.com, Circuitcity.com, eBay.com and JCPenney.com.

Traffic Swamps Sites

On the other end of the spectrum, sites that in recent days have been flagged for buckling under the strong holiday-season traffic include Mastercard.com and Macys.com.

Macys.com's home page faced slowdowns throughout Tuesday, taking, at its worst, about 38 seconds to load, compared with the usual 2 seconds, according to Web site uptime and availability tracker Gomez.

Apparently, while experiencing availability problems, Macys.com has been serving up a page telling shoppers that the site is crowded and that they have to wait until traffic decreases in order to be let in. An apparent screenshot of this page was posted by The Consumerist blog on Tuesday.

Meanwhile, Mastercard.com has racked up downtime of almost five hours between Nov. 9 and Dec. 20, equivalent to uptime of 99.5 percent for that period, according to Pingdom, which also tracks Web site performance. As such, Mastercard.com has performed significantly worse than sites from competing credit-card companies like Discover, Visa, Diners Club and American Express, all of which have had uptime above 99.9 percent during this period, Pingdom said Thursday.

Neither Macy's nor MasterCard immediately responded to requests for comment.