ComScore's estimates are in line with projections from other research firms, which have also said recently that holiday spending online is expected to show a solid increase this year.

'Expectations across all channels for this holiday season have been dampened slightly by high gas prices and wavering consumer confidence,' Gian Fulgoni, chairman of ComScore Networks, said in a statement. 'However, e-commerce will remain strong as consumers continue to shift more of their holiday spending to the online channel because of the Web's convenience and the savings available through its price-comparison capabilities -- not to mention the ability for consumers to save on fuel costs by cutting back on the need to drive to retail stores.'

The strong growth of e-commerce in traditional retail categories, such as apparel and accessories, home and garden, and jewelry and watches, indicates that consumers are now comfortable shopping for those products online, he said.

As consumers search for bargains, they turn to comparison-shopping sites and traditional search engines to help them find lower prices or hard-to-locate items, according to ComScore.

Comparison-shopping sites make up one of the fastest growing categories online, attracting more than 54.7 million visitors in October, up 52 percent from last year.