Thanks to the WSJ, here's a network-by-network guide to online viewing:

• ABC: Eight ABC series, including "Desperate Housewives," are available at ABC.com. Another series, "Ugly Betty," is sponsored by Brita LP, the filtered-water company. Each show is divided into four segments separated by 30-second, interactive Brita ads after which viewers must click to continue watching the episode.

• CBS: Full-length episodes from 13 different CBS series are available on its "Innertube" ad-supported broadband channel, at www.cbs.com/innertube/. The number of episodes available for each series varies from about a dozen for high-profile shows like "CSI," "Jericho" and "Survivor," to only recently aired shows for some series like "Shark" and "The Unit." Shows are separated into sections by nonskippable ads, and links are included to email the video and visit the series Web site.

• Fox: Fox on Demand introduced free, ad-supported shows this fall to its www.myspace.com/fox page and on MyFoxLocal station sites in 24 markets. Viewers can stream previously aired episodes of eight shows, including "Prison Break" and "Bones," which are updated after their TV broadcast. Some popular shows like "The Simpsons" and "House" aren't available, although a seven-minute preview of "The Simpsons" drew 1.4 million hits over three days in September. The MySpace site also provides interactive options, with links to the show's official site.

• NBC: Full episodes of six NBC shows, including "30 Rock" and "friday night lights," are accessible on its NBC Rewind video-streaming site at www.nbc.com/Video/rewind/. Like the other networks, shows are divided into segments by nonskippable ads. Every full episode is available for some shows, such as "Heroes." But some of NBC's most popular series, such as "The Office," "Scrubs" and "E.R.," aren't offered, other than in two-minute replays.

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