Comparison of software saving Web pages for offline use

A number of proprietary software products are available for saving Web pages for later use offline. They vary in terms of the techniques used for saving, what types of content can be saved, the format and compression of the saved files, provision for working with already saved content, and in other ways.
Video.
To save video embedded on web sites (e.g. YouTube), there are video download extensions for Firefox (including Download Helper) and Chrome.