Closing tab instances or single-tab windows not opened by javascript

PC browsers:
------------
Netscape 4.06 - Prompts the user about trying to close a window (I didn't see
this message, someone else tested it for me).
Netscape 4.80 - closes window without a prompt.
MSIE 5.0 - prompts the user.
MSIE 5.5 - Can't find anyone who has IE5.5 so untested there.
MSIE 6.0 - closes window without a prompt.
MSIE 7.0 - prompts the user for the first 3 buttons but will close the
window (if it's the only tab instance, otherwise will close the whole window,
not just the tab instance) without a prompt for the 4th button only.
Netscape 7.0 and 7.1 - closes the window without a prompt for the first 2
buttons, will report an uncaught exception regarding conversion of JavaScript
argument arg 0 in the javascript console for the 3rd button and will close the
window without a prompt for the 4th button.
Netscape 7.2 - will refuse to close the window for the first 2 buttons (javascript
console will notify "Scripts may not close windows that were not opened by script."),
will report an uncaught exception regarding conversion of JavaScript argument arg 0
in the javascript console for the 3rd button and will close the window without
a prompt for the 4th button.
Opera 7.x, 8.x & 9.x - closes the window in all 4 cases without a prompt.
Mozilla 1.4 - No prompt, just an information message "Scripts may not close
windows that were not opened by script." in the Javascript console.
Mozilla 1.5b - refuses to close in both cases: in the first case, the
javascript console will report the information message "Scripts may not close
windows that were not opened by script.". In the second case (Hikks), the javascript
console will report a conversion error (NS_ERROR_XPC_BAD_CONVERT_JS).
Firefox 2.0.0.13 - refuses to close the window (if it has only 1 tab opened) or
the tab in all 4 cases. The error console will report
"Scripts may not close windows that were not opened by script."
Safari 3.1 (build 525.13.0) - refuses to close for the first 3 buttons but will
close the window without a warning or a confirm prompt for the 4th button.

MAC browsers:
------------
AOL For Mac OSX v. 10.3 - closes the window without a prompt
IE 5.2.2 for Mac - closes the window without a prompt
Netscape 7.02 for Mac OSX - Does nothing, and after attempting to open, Netscape must be rebooted

All credits go to Randy aka "HikksNotAtHome" in comp.lang.javascript usenet newsgroup for this finding.

MSDN Reference on close method:
Invoking the window.close method on a window not opened with script displays a confirmation dialog box. Using script to close the last running instance of Windows Internet Explorer also opens the confirmation dialog box.

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