This code is probably a UTF-8 byte order mark in one of the files Joomla uses or includes (it’s only a zero-width no break space if it occurs inside a file). This character is a BOM and you can only see BOMs with simple text editors.
This error occurred when we open files in putty on live server. If we save the file sometime its Encoding type changed to UTF-8 BOM.
To resolve this error copy of your file content and paste into notepad++ and change its Encoding type UTF-8.