how should i use downloader add on while playing a video on YouTube?

If you want to save a video clip, that is a handy thing to have. I use Video DownloadHelper.

• https://addons.mozilla.org/en-US/firefox/addon/video-downloadhelper/

yesterday i got a software named mediaclip, just fabulous it is. guys u can download videos from YOU TUBE also. I'm really impressed. try this, if u have android device then you'll surely get this from market