"Somebody attached the chair to the floor."
Translation:Iu fiksis la seĝon al la planko.
I don't know how old this comment is, but it isn't "Lu" (lu) but rather "Iu" (iu). It is "iu" as in the "kiu, ĉiu, neniu, tiu" group of words meaning in some way about "someone".
Capital "i" (I) looks like an lowercase "L" (l). On my font, the lowercase "L" (l) have a super small hook on the bottom to distinguish from the uppercase "i" (I). Hope that helps!