Download Youtube videos Without any program. (Firefox Version)

In first place, open Firefox Browser, and click the little box saying "Firefox" in the left upper corner. 

Then, click Add-ons. And then type: Easy youtube downloader 6.8 (extension for Mozilla Firefox).
Click the first one, like in the pic. Install it.

Go to a youtube video. In the bottom of the video there will be a box saying: "Download". Click it.

Ending up, you have to select whatever you want. Audio formats and video formats or video (with music). 

And there you go! You can download the youtube videos you want, faster and easier with no extra installation.