I get no JavaScript errors in the console window. Debugging is easier in Firefox as the errors are all listed and if you double-click it jumps to the line causing the error in the source code (unlike IE, which often seems to get the line number wrong). It is also interactive as well.

The DOM inspector is also very useful.

I once remember reading somewhere that someone debugged their javascript in Mozilla - yet their site didn't work properly in Mozilla. Quite strange that.

I wonder what the cause of the error in IE is? Doesn't Windows Script Debugger know?