confirm(). But it might be used too much. I have been ordered from my client like this. “Not enough. Show the dialog box twice or thrice.” No kidding!!
Simple and very efficient. I love this style.
WordPress Admin Style
The background color of the delete button changes to red when mouseover. Nice effect! Users should attend to before clicking the button. Moreover, you could apply it to the existing apps with a few css code. (Although IE does not support :hover on elements other than links <a>, csshover.htc enables pretty much unlimited :hover usage in IE.)