No, user passwords should not be capitalized in a sentence unless it is the beginning of a sentence or part of a title. It is typically written in lowercase to differentiate it from proper nouns.
"It would usually be username, not user name."
First name: Wiki.Last name : user
An anonymous internet user gave some advice to a fellow user who was in need of it.
Nagato is the first user of the Rinnegan in naruto
A naughty user can be blocked from using this site.
Jody, a user on WikiAnswers, decided to enter a decathlon.
user profile.
Billy Bob was the first penguin user in Club Penguin.
(in relation to a drug user) He used to injurious levels.
Ctrl+alt+s
Tide tables can be found in an almanac.