Long pressing works for me. Have you checked the download folder? Does anything show up in the download list? Menu button > tools > download

No! There is no any downloading item shows after save. I think when I clicks save option there it show a directory to save target but there is no any popup comes.

you can also try the following: open firefox, type about:config into the address bar, search for the preference named media.play-stand-alone and toggle its value to false.

I have paste about.config in search bar but there is no showng media.play-stand-alone option.