Yes. HTML, CSS and Javascript are handled much the same as any flat HTML document. See "templates".
http://rtfm.modx.com/display/revolution20/Templates
MODx can use any HTML page as a template. All MODx does is manage the dynamic parts of any given page; menus, the content to be inserted into the the content area of the HTML, things like that.
While I don't work much with Revolution, you can view my Evolution manager (sottwell.com/manager/ guest -guestuser) and see how my site is structured and how everything works.
I was not referring to the aspx page, I was referring to the data collected. It has to go somewhere, and if you collect the data and save it (to database? to file?) with an aspx page, then any MODx page can retrieve it from storage. Likewise if MODx is used to host the forms it can save the data to database or file, and your aspx page can retrieve the data from storage.