I just edited a .html file using Adobe Dreamweaver, the charset is gb2312 since it's a Chinese website, then I used TextMate to edit the file, after I save the file, it was changed into utf-8 since the version of TextMate I'm using doesn't support Chinese. Is there any way I change the charset back to gb2312?
You can use Utilities -> Terminal and then sudo -s then Use the following command
iconv -f UTF-8 -t GB2312 oldfile.html > newfile.html
Change the charset in command accordingly.
Mac has a file version system like TimeMachine. You can browse the previous versions of the file. See if mac saved the previous version of your file.