Can a WORD document have a "."and sign its name? For example, I want to name it 2012.11.10. Is it okay?

The naming of such files is related to the system and has nothing to do with the WORD software you use. Now WindowsXP, Vista and Win7 all extend the support for file names, mainly supporting long file names. Because some characters are defined in computers and systems, they cannot be used in file names. Characters that cannot be used as file names are shown in the following figure!