Just how many tablets were sold this holiday season is still to be determined, but Chitika Insights, the market research arm of online ad network Chitika, believes it will prove to be  the biggest season ever for tablet sales  — and that iPad competitors will make small gains against Apple’s iPad, which will continue to dominate the tablet market. Chitika’s research is based on ad impressions from tablet devices  in the U.S. and Canada between Dec. 8 and Dec. 14.  According to the Chitika website, the research is conducted by “tapping into Chitika’s extensive network comprised of over 250,000 sites, totaling hundreds of millions of ad impressions each week.”

According to the research, based on tens of millions of tablet impressions, users of Amazon’s Kindle Fire family of tablets comprised 4.88 per 100 iPad impressions during the study period, a 4.25% share of all tablet Web traffic and nearly 20% above Kindle Fire’s 3.57% share registered in Chitika’s previous tablet market update.

Chitika also notds a usage share increase for Samsung’s Galaxy line of tablets, though a less impressive one, with Galaxy’s share of tablet traffic increasing from 2.36% to 2.65% from the latest to the previous report.

Google’s Nexus tablet line experienced an increase in usage as well, increasing from 0.91% in November to 1.06% in December, a 15% rate of growth.

Apple tablets continue to dominate usage, however. Apple iPad users generated over 87% of U.S. and Canadian tablet Web traffic, down slightly from just over 88% a month ago, according to Chitika.