ASP.NET ActionScript (getting Error on .as)

I have been building a basic .as script and email form for ASP.NET. My .as file keeps giving me this error

Error /Users/scottcarlton/Desktop/testingForm/ Line 11: Class and interface definitions cannot be nested.
dynamic class Popup extends MovieClip {

couldn’t attach the files, but here is a link to the .fla, .as, .aspx, and .aspx.cs

You help would be great.