Downloading from Youtube

In a previous version of Safari, I had somehow installed an addon that placed a "download" button under a video I was watching on Youtube. Pressing it, started a download of that video onto my computer.

I am not sure which version of Safari stopped this and I can't find any other way of doing a download.

Can anyone help.

I have vtried to go back to an older version of Safari, even changing the Safari folder in the User fold Preferences, but asI am using Snow Leoplard now, the older version of Safari won't work.