It looks like coffeekup isn't compatible with IE7 because indexOf isn't defined in Array.prototype.
I don't personally care, i can work around this issue. Is there a recommended script I can import to define some of these common functions for IE (and maybe other browsers)?
Fixed #71: indexOf not supported in IE7 (thanks @jaekwon).
Sorry, I should have been using CoffeeScript's in operator for arrays. Fixed in master.
Feel free to reopen the issue if necessary.