How To Download Web Videos To Your Computer Disk
So You'll Have Them If They Disappear From The Web

Videos on Youtube, Google, etc., can be removed at any time by the corporations that own and operate those websites. Once a video is gone, there's no way for you to see it there again.

However, if, while the video is still up on Youtube, etc., you download it to your own computer and store it as a file on your hard disk, then you can watch it any time you want using a video player program. And you can also write the video file onto a CD-R or DVD-R disk (one disk will usually hold many such files) and give them to other people so they can watch them too. Here's how to download videos:

First, install and use the Firefox web browser. If you're using Microsoft Internet Explorer, this is a good idea anyhow, since Firefox is better than IE in every way. You can get Firefox (which is free) here:

http://www.mozilla.com/en-US/firefox/

Once you're familiar with Firefox, install a video downloader add-on for it, called Video DownloadHelper, which you can get here:

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

That add-on will install on Firefox's navigation toolbar a little icon with three balls and a little v-shaped thingy. Whenever you go to a page with a video the balls will start to rotate. (If your balls start to rotate, that means it's a porn video.) Left-click on the v-shaped thing and you'll get a drop-down menu of the videos available on the page. Move the mouse cursor down to the video you want, and then move it rightwards to the second menu, which lists actions to take. Click "Download", and the video will be downloaded into the directory ~/dwhelper, unless you've changed the directory in the options. (If you right-click the balls, you get a menu with various control options for the add-on.)

It's a good idea to create various directories named for different subject categories, e.g., Politics, Science, TV, etc., and put your files in them so they'll be easy to find.

There are various programs that you can use to play the downloaded videos. Here are two that are free and run on Linux, Mac, and Windows:

VLC
MPlayer