Kohlberg Kravis Roberts & Co.'s Primedia Inc. agreed to buy About Inc., a Web site that creates Internet information guides, for about $500 million in stock, allowing the publisher of Seventeen and New York magazines to channel its content online. In a transaction that would unite two money-losing companies, Primedia said it will swap 2.34 shares for each About share. Although the agreement initially valued the purchase at $690 million, a 25% dive in Primedia shares sliced its worth to about $480 million. Primedia shares fell $3.81 to close at $11.44 on the NYSE, while About rose 31 cents to close at $24.19 on Nasdaq. About Chief Executive Scott Kurnit will keep his title and become chief Internet officer at Primedia. KKR, the world's biggest buyout firm, bought Primedia in 1989 and hired former NBC executive Tom Rogers last year to forge into new media.