Your username is always lowercase, and it MUST always be typed in lowercase letters when you are logging into a system. This is because to most computer systems, Jsmith is a different person than jsmith. This can be confusing because most home computers are not case-sensitive. When in doubt, it is safest to use lower-case letters. There are currently no systems on campus that will reject you for using lowercase letters in your username.
Passwords are once again case-sensitive.
However, they are not always lowercase. The case depends on what you type when you change your password. This is a great bit of added security if you use a random capital letter in your password. Imagine that someone watches you type in your password and sees you enter pookiebear . The odds are that they did not see you hit the shift key and actually you type pooKieBear .