I know now. If some one like me do not have good knowledge about uni-code, it would be a dizaster when shift from flash 5 to MX.

MX does not only "support" UNICODE, all the code manipulation is according to UNICODE encoding now. This shift might not cause trouble for English user. But definitely puzzles users that make Flash movie with Foreign characters when loadVariables.

For Chinese char "WELL", in Flash 5, the charCodeAt return A4AB and you can use "\uA4AB" to represent that char and the escape result is "%A4%AB";

Now in Flash MX, the unicode: the charCodeAt for the same char "WELL" return 4E95; You can use "\u4E95" to represent that char, and the escape result is "%E4%BA%95"; It conforms to the encoding that UTF described.

I have seen several post about trouble caused by this. Especially for those using Foreign characters. If we use Flash MX to edit our Flash 5 fla, the variable file that is used in loadVariables must renew by the unicode-escape function supplied by Flash MX. Also, if we use charCodeAt , it is different now.