[TYPO3] Change FE default language?

[Liu Jiansong]

Hi All,
I want to change default FE user interface language to Chinese(f.x. the 
"Username" and "Password" label of Login form), and found 
"typo3\sysext\css_styled_content\pi1\locallang.xml" controlling the FE 
user interface default language content, but after I changed some 
setting in this file, the FE renderer can't output Chinese normally, but 
some strange character.

Thanks
Liu Jiansong.