If you want to see which files have changed in your Dropbox account at a point in time, or if you want to undelete a file that you may have accidentally deleted, you can do both of these things through the web interface.
View the video below, or click here to watch it on YouTube. If you are able to, I recommend that you watch it with HD turned on.
This video on checking which Dropbox files have changed is part of a series of quick videos on paperless tips and topics. View more in the series here.