Originally Posted by HDQDD

Not necessarily. At least not on the server side. Passwords aren't stored (server side) in plain text. They're one way hashed (most likely with a salted key) before they go into a database (usually in the form of a long hexadecimal string). Then the next time the user logs in, the input password goes through the same hashing algorithm and is compared to what the users hashed password is in the DB (if it matches, then the user is authenticated). The reason it's done this way is because even if someone gets access to the whole database, the passwords, when properly hashed, will be almost worthless (or at least take a while to crack, at which point they won't have much value). With ever greater processing power and more secure hashing techniques, this is a continual cat/mouse game with hash algorithms.

It might make it harder to guess a password with complex chars on the client side, but any reputable site limits the amount of guesses before they lock out an account, so it's really a moot point. Just don't use easy passwords like Password1, DWKWIA!!, etc. and you'll be fine.