The technique used for this is called imagemapping. You simply specify which areas of the image should link to where. In the above example we only used rectangular imagemappings. In the examples above we only used rectangular imagemappings. There are excellent tools out there to help you create imagemaps.
Nobody calculates the coordinates by hand.
If you want to use imagemaps on your site you will need to get a program that will allow you to simply drag the mouse over the areas you want to work as links. Linking to bookmarks works very similar to linking to pages. Usually bookmarks are used when you create pages with considerable amounts of text. You would typically make an index at the top of the page linking to the bookmarks that has been added to key-places in the text that follows. If you want to customize the new window as to which buttons, menus etc. should be available and which size it should have, you will need to do it with javascript .