Usefulness in web design is paramount. IKEA has done it right. Check out this great example of an image rollover.
We’re going through a refi and needed to setup an online account with Fremont Bank.
They have the most impressive Password form verification. Upon clicking the password text box, a tooltip expands below to list the verification parameters. As you type, the characters change green/red according to the correct syntax.
What makes this a great UI/UX example is that it doesn’t take up any extra real estate on the page, it’s activated automatically and it dynamically or actively verifies the information. Brilliant!