Webpage won't recognize CSS for Internet Explorer

I have finally figured out how to load CSS files according to the browser type....except for one....Internet Explorer. The funny thing to is, while testing, I put an alert statement to show which browser was being used. I'm using Internet Explorer 11, however, the message pops up "Netscape" before it actually loads the CSS file. I'm not sure why it's doing that and I'm not sure how to tell which CSS file is being loaded. Is there anyway of telling for IE which CSS file was loaded?

Thanks,