I get NULL retrieving JSON from especific website

I get NULL retrieving JSON from especific website

References

Reference NO 1

http://stackoverflow.com/questions/11069894/null-pointer-exception-while-retrieving-json-object

Reference NO 2

http://stackoverflow.com/questions/4377220/i-want-get-one-specific-entry-from-json-data-array-and-do-some-modification

Reference NO 3

http://code.google.com/p/google-web-toolkit-doc-1-5/wiki/GettingStartedJSON

Reference NO 4

http://www.salesforce.com/us/developer/docs/apexcode/Content/apex_methods_system_jsonparser.htm

Reference NO 5

https://dev.twitter.com/docs/api/1/get/users/search

Reference NO 6

http://www.accella.net/android-http-get-json/

Reference NO 7

http://google-styleguide.googlecode.com/svn/trunk/jsoncstyleguide.xml

Reference NO 8

http://cypressnorth.com/programming/cross-domain-ajax-request-with-json-response-for-iefirefoxchrome-safari-jquery/