[itimpi]

With dropbox you always have a local copy of your files as well as the copy in the 'cloud'. You actually work with the local copy of files, and behind the scenes Dropbox is syncing changes to the 'cloud' copy which also makes the changes visible to other machines syncing to the same dropbox account.

As long as you have been online so that your local dropbox files are current, you can work off-line and any changes you make will be synced as soon as you come back on-line. The only issue is to make sure you have come online so that changes can be synced before you start working on the same dropbox files on another machine.