Howe do you go about storing large volumes of data persistently in a browser. Cookies are no good because the data gets sent back to the server so it will break most http connections at about 4K. But there are a number of newer mechanisms appearing. IE5+ has had userData ( http://msdn.microsoft.com/workshop/author/behaviors/reference/behaviors/userdata.asp ) for a while, Firefox2 has DOM:Storage from the HTML5 spec (see http://www.whatwg.org/specs/web-apps/current-work/#storage and http://developer.mozilla.org/en/docs/DOM:Storage ) and then there are things like halfnote ( http://aaronboodman.com/halfnote/ ). We appear to moving rapidly to a state where the browser is becoming an offline client, but none of this works for FF1.5, Safari and others.
With a footprint of 1px by 1px and 4K who is going to notice it ?
RWiki will be using this for autosave functionality.