IE 11 using Javascript 1.3

I have a web project that has to work on multiple browsers. When I use the following link to test the javascript versions this is what I get:

Link: http://jsfiddle.net/Ac6CT/

For IE 11 I get 1.3 (my code breaks)
For IE 9 on Vista I get 1.7 (my code works)
For Chrome on Windows 8.1 (same machine as IE 11 above) I get 1.7 (my code works)
For FireFox on Windows 8.1 (same machine as IE 11 and Chrome) I get 1.5 (my code works)

So the question is why is IE 11 only running javascript 1.3?  Can I set this to a higher version?

The code that is breaking is str[0] which is undefined in 1.3 but works in all of the later versions.

I would like to change the javascript version instead of my code if at all possible.

Thanks,
Susan G. Conger

BFC Associates