Black Friday and Cyber Monday are just around the corner, and marketers are likely hoping to cash in on these major shopping days. A new holiday ecommerce forecast from comScore suggests marketers have a lot to look forward to this season – online sales are expected to grow 11 percent over the same period last year.

According to the report, holiday retail ecommerce during the first 21 days of November 2010 exceeded $9 billion. This marks a 13 percent increase over the corresponding period last year, when sales hit 7.95 billion.

The positive start to this year's online holiday shopping leads experts at the firm to believe sales for the rest of the season will outperform earlier expectations. ComScore predicts that online retail spending for November and December will reach $32.4 billion. This represents an 11 percent increase over the same period last year.

Marketers hoping to catch their share of these sales may be interested to learn that one-third of consumers say free shipping is "very important" to their purchase decisions. Plus, increased spending may be linked to marketing promotions, as 36 percent of respondents claim they are finding more discounts and sales this year compared to 2009.

No matter the strategies marketers use to attract online shoppers, they stand a good chance to make significant ecommerce sales this holiday. EMarketer's online holiday sales predictions are even more optimistic than comScore's forecast. As Brafton reported, eMarketer anticipates online holiday spending will reach $38.5 billion.