Warning: a pet peeve follows.
Way, way too many programmers are in love with the words "OK" and "cancel", as in the dialog box "You are about to format your hard drive and set fire to your house. [OK] [Cancel]."
Originally, it made sense: this was your chance to either proceed with an operation or cancel it altogether. But those words have become synonyms for "yes" and "no", and that's a problem.
Take this example:
(I've blocked out the name of the offending Firefox extension because, well, why single them out when there are so many other offenders?)
This box popped up while I was trying to register a domain name. It was asking me a question: did I want something to happen? And the logical answers are either "yes", "no" or (and this is asking too much from most apps) "I'm not sure; tell me more".
But "cancel"? That could mean anything from "cancel saving the username" to "cancel submitting the form" to "Stop the Internet: I want off." A few seconds of reflection later, and the likely meaning is clear... but as Steve Krug pointed out so famously, making users think (at least about interface choices) isn't a friendly thing to do.
There are still times when "OK" and "Cancel" make sense; I don't suggest jilting them altogether. But when you're asking a yes/no question, what possible reason could you have for not offering users the ability to give a yes/no answer?