Spliting a String

var data = '{"CTS":"0,51,52","lastTopic":53,"questions_answered":["3","2","4","1","9"],"scoreArray":[],"06_01":20}';

// work on modern browser, check this page : http://caniuse.com/#search=JSON.parse
// for old browser download and include the following javascript in your page :
// https://github.com/douglascrockford/JSON-js/blob/master/
// <script type="text/javascript" src="path/to/your/js/folder/json_parse.js" ></script>
var json = JSON.parse(data); 

alert( json["06_01"] );

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test page : http://jsfiddle.net/tBnjf/2/

How would I code for older browsers especially IE7 ?

It works for the rest

read the code in my first post, line 4,5,6...

Sorry, I read the above lines for older browser. Confusion was in the json_parse.js, the sample code was like this

myData = json_parse(text, function (key, value) {..

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your code was

var json = JSON.parse(data); 

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Also do I have to detect older browsers ?