Pop quiz: See if you can guess which password is more secure -- Tr0ub4dor&3 or correcthorsebatterystaple. The first password is a jumble of letters (both uppercase and lowercase), numbers and characters, with a few numbers substituting for letters. The second is a string of four common words -- correct horse battery staple.

Because sometimes a tiny character can make a huge difference!
/ forward slash
Leans forward. Forward slashes are for Internet addresses.

: colon
Also used in Internet addresses. Traditionally this mark informs the reader that what follows the mark proves, explains, or lists elements of what preceded the mark.