It goes without saying that strong passwords are a must in today's technology environment. The strength of a password is based on its length, the complexity of its makeup, and its lack of predictability. As it turns out, password length is the most important of these factors, although adding mixed case (i.e., upper- and lowercase letters), numbers, and, when allowed, unusual characters such as #, ^, or *, also adds strength.
Passfault.com is a nifty tool that will estimate how long it would take for a hacker/cracker to determine a password (assuming cracking technologies don't evolve and improve). For example, let's say you use "caveman" as your password. According to Passfault, that password could be cracked in less than a day if it fell into the wrong hands. So, how can you make it stronger? Let's start by changing the length. Simply by doubling up each of the letters—ccaavveemmaann—you would have a password that, according to Passfault.com, would take a hacker 369 centuries to crack. Yet, you'd still have a password you could remember! Now let's add a few numbers to it. Let's say you live in New Haven, IN, and your Zip code is 46774. By putting a portion of the Zip code on either side of the password (i.e., 467ccaavveemmaann74), you would have a password that would take a hacker a whopping 47,560,683 centuries to crack!
The short of it is that if you use a short password you do not have a very strong password.