Migrating Bookmarks From My Web:
We have consolidated the features of the original My Web into the new Yahoo! Bookmarks. The first time you visit Bookmarks, your original My Web bookmarks are automatically migrated to the new Yahoo! Bookmarks.
Migrating Bookmarks From Yahoo! Toolbar:
Once you click the bookmarks icon in Yahoo! Toolbar we automatically copy all your previously saved Yahoo! Bookmarks into the upgraded Yahoo! Bookmarks. This happens only one time.