1. A computer-implemented method performed by data processing apparatus, the method comprising: identifying a user; receiving user input from the identified user through an interface associated with a web browser of a client device, the user input indicating a modification to a set of bookmarks for the identified user; in response to receiving the user input: modifying a set of bookmarks stored for the identified user in a client-side storage of the client device; and synchronizing the modified set of bookmarks with a server-side bookmark storage system configured to synchronize bookmarks for the identified user with one or more other client devices.
7. The computer-implemented method of claim 1 , wherein synchronizing the modified set of bookmarks comprises synchronizing a hierarchy of bookmarks within the modified set of bookmarks.