Safari plugin warns when closing multi-tab window.
TabStop is a SIMBL plugin, available in several different languages, that displays a warning when you attempt to quit or close a window in Safari that contains multiple tabs. Very handy, if you're used to keeping dozens of tabs around and you're tired of accidentally Command-Q'ing instead of Command-W'ing.
What's new in TabStop
Includes Dutch localization (thanks, Ronald Lamars!)