You're browsing a friend's home page and a short text about mummification appears just under his name. Don't panic-it's art. You're experiencing The Impermanence Agent, devised by Noah Wardrip-Fruin, artist in residence at New York University's Media Research Lab. Wardrip-Fruin's work is one of two disturbing new interactive artworks that treat the themes of time and memory.

The Impermanence Agent appears as a small window with a scrolling story. The agent intercepts the Web pages you're browsing and uses text from your readings, over time, to modify the story. The Web pages you view also get altered. A funerary image might pop up in The New York Times. The banner title of Arts and Letters Daily might appear eroded or decayed, as if weathered by some electronic rain or television snow-all with the suggestion of the damage time does.