Pages added to a Qu-s note are stored in platform-independent WebArchive format.
http://www.diigo.com/list/grahamperrin/WebArchive?v=p for an overview of support for this format.
Any page browsed within Qu-s can be added to a list.
For each addition of a URL (comparable to a bookmark): a local snapshot is stored in WebArchive format.
In a Qu-s project, a list may include multiple bookmarks/snapshots and other forms of data.