If maybe you wanted to download YouTube videos to your PC but without an Internet connection, wherever and whenever, then you can use the following ways.
An extension in Firefox called Keep the Tube, is now also compatible with the Chrome browser, Internet Explorer, and so forth. It is more interesting than Keep Keep Tube Tube is not only to work with YouTube, but could also for CollegeHumor, Facebook, Google Video, Metacafe and other video sharing sites.
When you see the video that you like, just click on the icon Keep in Firefoc Tube or in part of his bookmarks. From there, you'll see on the page Keep the Tube where you can download the video in one or more formats and file size. It would be better if the download in MP4 format and use the highest resolution.
FLV format, it will require a special player, while able to work in Divx MP4, QuickTime and player in general. In addition, the MP4 format can also be played with a good smartphone