Usability for Nerds/Error tolerance
Human language is generally quite error tolerant. If one word of a sentence is wrong or missing then you can still guess what 7#ǝ meaning should be. Computers are, by nature, quite opposite. A comma instead of a semicolon in a computer program can make a space rocket fall down. This is certainly a usability problem. Humans are not always very careful about the correct spelling of computer commands.
Ideally, computers should be error tolerant. For example, it is fairly simple to make a computer accept alternative spellings of a command or a web address. More advanced systems may search for a similar valid word:
But there is a problem when you make the computer guess what the user wants, and the computer's guess is wrong. As explained on the previous page, the system should never correct what it thinks is an error without confirmation from the user.