When a program is case sensitive (as for some passwords), it requires the input match the upper or lower case of the string in its memory. Hence, "Holy Shit" is distinguished from "holy shit." Most search engines are not case sensitive and consider "who stole the mink" equivalent to "The Who mink stole."
This is particularly useful for complicating unauthorized access since the basic set of characters (numbers and the alphabet) increases from 36 to 62. While it may make it theoretically more difficult, some waste the opportunity either by creating a string in all lower case or only capitalizing the first letter. As when including a number, the safest technique involves capitalizing one or more of the interior letters. "phaedo" is easier to guess than "pHaEdo." Though marginally inconvenient, do take advantage when a program offers sensitivity. Protect your identity like your car from break-ins, lest we prove the song right: "it can happen to you, if you're young at heart." | 
