Blueimp jQuery File Upload returning html instead of json-Collection of common programming errors

I downloaded the blueimp Jquery-File-Upload plugin, and outside of configuring it to use my server ( in js/main.js ) and changing the premissions on the upload directory it is the default.

When I select a file and click upload in chrome it says:

Error SyntaxError: Unexpected token <

In firefox it says:

Error SyntaxError: JSON.parse: unexpected character

I examined the difference between using it on my server and on the demo server, on my server in firebug the POST return is the entire index.html: