Firefox 3 has “online” and “offline” events. That’s javascript-speak for saying: now your webpage can know when you’re offline (and hence queue it’s actions) and when you’re online (and then send all the queued actions to the server).
In other words, offline apps will be possible in Firefox 3. Hopefully we’ll soon see experimentation and then an open js library to enable easy offline app-making (like js libraries now make ajax easy for dummies). IE is the only problem factor then.
Peter Van Dijck 
add dom-storage (cfr. http://developer.mozilla.org/en/docs/DOM:Storage) to that and we’re really on a roll!
Would this mean something like Google Docs / Spreadsheets could function without internet and save / update when access is restored?