That's standard JavaScript (to me at least). I don't know why it would not work with IE. I'm a systems programmer by trade. Being newish to JavaScript, perhaps I made a mistake, so let me know any ideas you have to make it work with IE, or edit it yourself. It's GPL code.
Edit: Thanks to timb it now works with IE 9. Thanks!
in the html of http://16s.us/sha1_pass/js/ add <!doctype html> to the top. this will prevent "quirks mode" in IE and String.prototype.trim will reappear.
What was it you were saying about walled gardens?