I’ve been watching videos from Reboot, a web conference in Denmark. Mark Hurst tells some interesting stories about usability lessons from the web. My favorite: when your checkout screen prompts for a username and password, some newbie users will type in their AOL username and password. Why? They’re not reading the text that says “returning customers, type your username and password.” More proof that people don’t read, but also evidence that people will assume the simplest possible program model — i.e., that their new AOL password works everywhere — until they learn otherwise.

(Feel free to fast-forward over the pompous negroponteisms like his slide titled “This is the Age of Bits.”) The video is here.

Techinterview: How does one find a loop in a singly linked list in O(n) time using constant memory? You cannot modify the list in any way (and constant memory means the amount of memory required for the solution cannot be a function of n.)

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I'm Joel Spolsky, co-founder of Trello and Fog Creek Software, and CEO of Stack Overflow. More about me.