Just create a variable on main time line called
id, & in your movie you can use it. But don't forget that in design time, this wont work. as the ?id=something would be given in html page. So follow these steps:
in your flash movie's main timeline, add this code:
var id;
_root.someTextfield.text = id;
Export the swf & the html file. Open the html file in any text editor, search for filename part & replace the moviename.swf with moviename.swf?id=mazhar & save the html file, now preview this file in any browser