I approve of both changes; the focus should be on the words. (I’m also glad you mentioned a while back that you were going to eventually insert the words where they chronologically belong instead of keeping the “this has been antedated to...”; it greatly reduces the twitching I experience on encountering such statements.)
cosplay, n. Cosplay is the practice of dressing up as a character from anime, manga, or other form of entertainment. The word sounds like it comes from a blend of costume play, and in a way it does, but it immediate source is the Japanese kosupure, which is a blend of kosuchumu-pure, which in turn is from the English costume play. Kosupure appears in Japanese by 1982.
Very minor, but the second occurrence of “costume play” needs to be in italics as well.
web site, n. Not much needs to be said about this one.
Except that it’s now written as one word except by fuddy-duddies (and people forced to use fuddy-duddy style guides—happily, the new Chicago has made the switch).
year 2000, n. People were starting to talk about the problems that would be encountered by computers and legacy software systems when year 99 rolled over into year 00 seven years hence.
I don’t understand the rationale for this entry. Isn’t this just the normal phrase “year 2000,” which has doubtless been used for centuries, mentioned in the context of computer problems?