Although you set your page to be charset=GB2312, your page is not encoded in GB2312. You see, if you use Notepad in Englihsh enviroment, the file is usually in UTF-8. Maybe the latest version of Notepad can let you select which encoding way you want.

I know little about 南极星, but in these days, the editors can support various encoding method. So, just throw 南极星 away.

ps, you can try emEditor.