1. Click the menu button and select Preferences.
2. Select the General panel.
3. Scroll down to the Offline section.
4. Select the Enable offline mode checkbox.
5. Select how much disk space you want to use for offline content.
6. Click OK to save your changes.
To view bookmarked sites offline:
1. Disconnect from the internet.
2. Open Firefox and click the menu button.
3. Select Bookmarks >Show All Bookmarks.
4. Select the Offline Bookmarks folder in the sidebar.
5. Click the bookmark you want to view.
Note: Only HTML files can be viewed offline.