"Do you have a nickname?"
Translation:Ĉu vi havas kaŝnomon?
According to my knowledge and reading in Esperanto and the dictionary by Wells; kasxnomo means pseudonym, while kromnomo means nickname.
According to reta-vortaro the diference between 'kaŝnomo' and 'kromnomo' or 'alnomo' is that the first is seft-assigned while the others are gived by friends.
As internet nickname are self-assigned, than 'kaŝnomo' is a better translation although both can be applied.
Considering the Internet theme of this section, I think that it is meant to be "nickname" in the online sense, i.e. a username.
So it needs to be changed to username, because usernames and nicnames are entirely different things.