Common error in json string

Using single quote ' instead of using double quote " when wrap the string.

JSON strings should be wrapped with double quote (http://json.org/)

A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A character is represented as a single character string. A string is very much like a C or Java string.