The challenge is simple: roll a d20. You have to write for however many minutes come up. If it's a 5, write for 5 minutes; if it's a 15, write for 15 minutes. 1 and 20 aren't anything special, other than the fact you're not going to get many words out of a 1, but a lot more out of a 20. Repeat with each dice until you've used each dice once.

The actual challenge, however, is this: you can't browse the internet until you finish. You can take a break between dice to get a drink or a snack or whatever, but you can't use the internet. No, not even to update your wordcount.

If you don't have dice, you can use an online dice roller. On average, with 8d20 you'll end up writing for about an hour and a half. I usually get between 1500-3000 words out of this challenge, depending on how many minutes I roll.