Codepage就是各国的文字编码和Unicode之间的映射表。
Code page: An ordered set of characters in which a numeric index (code point value) is associated with each character. This term is generally used in the context of code pages defined by Microsoft Windows 3.1 or MS DOS and may also be called a "character set" or "charset."
http://msdn.microsoft.com/en-us/library/cc194760.aspx
比如简体中文和Unicode的映射表就是CP936。以下是几个常用的codepage，相应地修改上面的地址的数字即可。
codepage=932 日文; codepage=936 简体中文GBK; codepage=949 韩文; codepage=950 繁体中文BIG5
codepage=437 美国/加拿大英语
codepage=866 俄文
codepage=65001 unicode UFT-8
最后一个65001，据个人理解，应该只是一个虚拟的映射表，实际只是一个算法而已。
Related resource:
The differences exist between the appearance of squares, question marks and garbage codes when localized strings can not be displayed properly?
(1)
Reason: Indicates select font can not display characters
(2) Question Mark (???)
Reason: Indicates Unicode to code page conversion failure
(3)