"By default Publisher sets the tab order of the form controls (fields) in
the order in which the controls are added to the page. The Arrange
(front/back) feature can be used to set an explicit tab order in a form.
This is done by selecting each control in the order you want the tab order
to follow, and setting it to "bring to front". In v2003 you can right click
the control and select Order, Bring to front. In v2002 you can use Alt + F6.
Or just use the Arrange menu."
reference: Publisher web publication forms 101:
http://msmvps.com/blogs/dbartosik/archive/2006/01/07/80564.aspx
DavidF