The link is to a really charming interview with Donald Knuths, everyone's computer science hero.
Knuth gives out checks for $2.56 to people who find errors or typos in his books.
I myself received a check for $1.28 and another for $2.56 from Knuth when I was in college. These checks were for typos in his TeX and MetaFont books. I was so poor back then that I cashed them. In fact, I was so poor that even though I thought about making copies of the checks, I decided the $0.25 that would cost was too much.
Here's an errata page (scroll down) from Knuth's page at Stanford.
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