function base64_decode( data ) {
    // http://kevin.vanzonneveld.net
    // +   original by: Tyler Akins (http://rumkin.com)
    // *     example 1: base64_decode('S2V2aW4gdmFuIFpvbm5ldmVsZA==');
    // *     returns 1: 'Kevin van Zonneveld'
 
 
    var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var o1, o2, o3, h1, h2, h3, h4, bits, i=0, enc='';
 
    do {  // unpack four hexets into three octets using index points in b64
        h1 = b64.indexOf(data.charAt(i++));
        h2 = b64.indexOf(data.charAt(i++));
        h3 = b64.indexOf(data.charAt(i++));
        h4 = b64.indexOf(data.charAt(i++));
 
        bits = h1<<18 | h2<<12 | h3<<6 | h4;
 
        o1 = bits>>16 & 0xff;
        o2 = bits>>8 & 0xff;
        o3 = bits & 0xff;
 
        if (h3 == 64)      enc += String.fromCharCode(o1);
        else if (h4 == 64) enc += String.fromCharCode(o1, o2);
        else               enc += String.fromCharCode(o1, o2, o3);
    } while (i < data.length);
 
    return enc;
}