SAN FRANCISCO — On the Internet, nothing travels faster than a tip on how to score a bargain. Especially in an economic downturn.

Tami Chappell for The New York Times

Tavon Ferguson, 25, says she planned her wedding with coupon codes “at a price that nobody would even guess.”

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Steve Kagan for The New York Times

When Scott Kluth started CouponCabin, some retailers were displeased. Now stores send him a thousand codes a week.

With online retail sales falling this month for the first time, Internet merchants are offering steep discounts to anyone willing to punch in a secret coupon code or visit a rebate site for a “referral” before loading up their virtual cart.

Shoppers obsessed with finding these bargains........ www.nytimes.com