Access flags (what the admin can do):
a - immunity, b - reservation, c - kick, d - ban, e - slay, f - map, g - cvar, h - cfg, i - chat, j - vote, k - sv_password, l - rcon, m..t - custom, u - menu, z - user.
Account flags (identification):
a - disconnect on bad password, b - clan tag, c - steamid, d - ip, e - no password check, k - case sensitive name.
Typical:
SteamID: "STEAM_..." "" "abcdefghijklmnopqrstu" "ce"
Name+password: "Player" "pass" "abcdefghijklmnopqrstu" "a"