MACROMEDIA FLASH MX 2004-ACTIONSCRIPT LANGUAGE Reference page 744

// Get the user of the kookie and go to the frame number saved for this user.
if (my_so.data.user != undefined) {
this.user = my_so.data.user;
this.gotoAndStop(my_so.data.frame);
}
The following code block is placed on each SWF file frame:
// On each frame, call the rememberme function to save the frame number.
function rememberme() {
my_so.data.frame=this._currentframe;
my_so.data.user="John";
}
744 Chapter 2: ActionScript Language Reference