Now you'll add a navigational aid to your form—a tabbing chain that allows viewers to use the Tab key to move between form fields. To create a tabbing chain, you specify the order in which the form fields are selected by the Tab key. Adding a tabbing chain should be the last thing that you do to your form, after you are satisfied with its layout.
Note
Some Web browsers will automatically allow users to use the Tab key to move between text fields. In addition, some browsers only allow users to use the Tab key to move between text fields and not other types of form fields. Also, be aware that the tabbing order that you create may or may not be recognized, depending on the browser and which version the visitor is using.