I'm generating a printer-friendly page that automatically opens the browser's print dialog box upon user visit. Is there a way to close the window if the user presses "Cancel"?
window.print() has no standards; its operation is a grab-bag from browser to browser. Futhermore, to my knowledge, in no browser implementation does it pass information back. You cannot determine how the user responded to the print dialog via JavaScript.
That said, it would seem the only point of the print-friendly page would be to print. Perhaps you can close the window after prompting to print, regardless of how the user responded?