Online shopping has increased dramatically in this, the first big holiday season on the Internet, but analysts also report a sharp rise in customer dissatisfaction.

Figures from research firm Media Metrix show traffic at online stores up 45 percent this month from last December.

At the same time, customers' rating of on-time delivery, on a 10-point scale, fell from 8.16 in October and the first half of November to 7.91 in the three weeks ended Dec. 5, according to BizRate.com, a company that surveys 30,000 online shoppers each day.

Overall satisfaction was down by a similar amount.

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