In emacs 23.x, the default location for bookmark is at 〔~/.emacs.bmk〕.
In emacs 24.x, it is 〔~/.emacs.d/bookmarks〕.
So, if you are upgrading to emacs 24, you might want to move and rename your bookmark file.
The default location is controlled by the variable “bookmark-default-file”.
For the basics of bookmark, see: Using Emacs's Bookmark Feature.