n. A person who watches video content online or on a computer, or who combines regular TV watching with related digital content.
Since July 10, the Pepsi-Cola brand has been presenting to computer users "The 9," a program produced by the Yahoo Studios division of Yahoo that can be watched at 9 a.m. Monday through Friday on the entertainment section of

The fast-paced show, which lasts five to six minutes, offers "viewsers" — as Mr. Weiner calls viewers of online programming — a roundup of nine offbeat video clips from various Web sites, and invites them to vote for a "Pepsi 10th," a favorite clip of their own.
—Stuart Elliot, “The Plot Is the Pitch,” The New York Times, September 01, 2006
Now, the technology is so advanced and changing, even the industry word for a person who watches TV has changed, Heizman says. It used to be "viewer." The new word is "viewser." Today's viewser doesn't necessarily watch TV. He might click to the station's Web site, instead — He might call the Weatherline. He might catch the news on his cell phone.
—Ron Wolfe, “Leslie Anne Doubleday Heizman,” Arkansas Democrat-Gazette, June 25, 2006
1995 (earliest)
So, are we all about to turn into armchair film directors? Well, no: we are not at the stage where a movie and its characters are just raw material, waiting to respond to all our commands. Right now, what interactive movies offer is a series of choices at various points in the plot which will send the chooser in a variety of directions until they hit one of the predetermined end-points. So the idea that the "viewer" is truly participating is somewhat misleading at this stage of devlopment and some interactive film makers believe a term like "viewser" (from "viewer" and "computer user") would be more appropriate because the state of the art is more to do with combining features of both films and computer games.
—Greg Roach, “Into the vortex,” New Scientist, September 23, 1995
I found several citations prior to September 23, 1995 that use the word viewser. However, the fact that none of them explain the origins of this unusual word (as the earliest citation does, above), leads me to believe that they're all just typos. (The w, e, and s keys are bunched together on the keyboard, so I'm guessing this "typoneologism" is quite common.)