Google and other web application providers have known this since day one, but now thanks to Google Gears, Docs will be getting an offline version. Google Docs offline will allow you to continue working on a document using your browser even if you have lost internet access by adding a local version of your document list and the editors (for now limited to view and edit text documents). Once you get back online your offline documents should automatically sync. This is an important step for Google if they want to face Microsoft, but now that they have stepped in their turf it will be interesting to see how the industry reacts.
Google Docs offline will be rolled out to a limited number of users initially only in English, but they hope to have the service available to all users sometime during the next few weeks.