Bitcoin address
Just above the "footnote", at the bottom of the xkcd, is tiny print reading:
- BTC 1FhCLQK2ZXtCUQDtG98p6fVH7S6mxAsEey
The later portion (bitcoin address) also used to appear at xkcd.com/bitcoin/. "BTC" is the abbreviation for bitcoin.
This is apparently xkcd's bitcoin address, perhaps the high-tech equivalent of a tip-jar. Details about this can be seen in several places.
xkcd.com/bitcoin/ has since changed to 14Tr4HaKkKuC1Lmpr2YMAuYVZRWqAdRTcr
and is currently a 404. This second BTC address may belong to xkcd[citation needed]. Until confirmed, do not donate, as it may be that the page has been maliciously modified as the footnote has not been changed. Before those two adresses, it used to say 1Lg2rvxbBPC8jp2YJoV5xL7sdyTjueMUot
.