How come the characters of firefox is so ugly

How can I sove this problem?
Remarks: The firefox is installed in linux

Thanks in advance~

The following is my screen shot of this problem
附件: 您所在的用戶組無法下載或查看附件
字體問題? Windows版本都要自己改先靚


我玩console only - text mode

He told me that he didn't know how to fix this problem too! Anyway, thank you:)