For example, during December 2008, ABC's "Lost" had the most unique viewers of any network show: 1.425 million. "Saturday Night Live" grabbed the second spot at 1.1 million.

While "Lost" has been a good-rated show over the years, it has never had consistent top ratings. Moreover, "Lost" wasn't even on ABC during the month of December, signifying that perhaps viewers were looking to catch up.

"SNL" runs in late-fringe on Saturday night, typically where shows have lower ratings than programs in prime time. NBC grabbed massive audiences for "SNL" leading up to the presidential election, in part due to Tiny Fey's impersonation of GOP veep candidate Sarah Palin.

The next two spots were "Grey's Anatomy" at 879,000 and "Desperate Housewives" at 723,000. Places five through 10 went to NBC's "Heroes," ABC's "Ugly Betty," ABC's "Samantha Who," ABC's "Scrubs," CBS' "Survivor" and ABC's "True Beauty."

Nielsen analysis suggests that many shows were not offering new episodes in December (apart from ABC's "True Beauty"). Viewers were looking to familiarize themselves with programs before a return to new shows in January.

The network Web sites included ABC.com, CBS Television, CWTV.com, Fox Broadcasting and NBC.com. The rankings did not add Hulu, which currently does not report Nielsen's VideoCensus data.

Nielsen says the data for unique viewers included those who viewed a full episode, part of an episode or a program clip during the month.

Top 10 Online Broadcast TV Network Entertainment Programs* for December 2008 ranked by Unique Viewers (U.S.)