When I tried some AS codes from my previous works today in Flash 8, it didn’t work properly but it did work fine before. Finally I find out the problem pertains to variable declaration.
In previous version of Flash and Flash player 6, the following code is valid:
var t;
t+=10;
trace(t);
// Output: 10
However, it won’t work since Flash MX 2004 or Flash Player 7.
Therefore the code need a simple modification:
var t=0;
t+=10;
trace(t);
// Output: 10
I think most people know about the stricter rule of variable declaration now in Flash. So be careful when you want to publish your old codes with new Flash.