I noticed a couple of announcements side by side the other day, saying programs had been called off because of inclement weather. However, one had cancelled (with two L's) and the other had canceled (with one L). It made me grin, so I took a photo of the pair of announcements. While canceled and cancelled are both acceptable for the past tense of cancel, the version with one L is more common in American English, while the version with two L's is more common in British English. So both of these spellings are correct. How do YOU spell that word? I actually spell it with two L's. Maybe that means I've read a lot of British literature in my life.
NOTE: I googled "plural of the letter L" to see whether or not to use that apostrophe. Huh, the plural can be L's or Ls (for capital letters), l's or ls (for small letters). It seems more confusing to me to leave out the apostrophe, so I put it in there. Notice that "ls" looks like capital i with a small s. That spells the verb "is" and isn't what I want to say.