Folders are often depicted with icons which visually resemble physical file folders. Most computers organize files into hierarchies using folders, directories, or catalogs. These other folders are referred to as subfolders. In addition to files, folders, volumes and other file system objects may have attributes. Live icons can display the content of folders and files themselves rather than generic icons. Limits AutoPlay's content search to only those folders listed, and their subfolders. This has the effect of establishing directories (i.e., folders) and files within those directories. Users can add additional toolbars that display the contents of folders. Dropbox users can share documents as links or as shared folders. Multiple mailbox support also allows servers to provide access to shared and public folders. The incomplete file prevented Opera users from emptying their "Junk E-mail" folders. Many email clients allow the creation of folders to organize email. The navigation pane contains commonly accessed folders and preconfigured search folders. Users can now mirror desktops or other folders. Registry "keys" are container objects similar to folders.