Just to add to this, if you can get your hands on Expression Web then thats good and I would start using it. It is 100% compatible with your Frontpage 2003 sites and has many new features as well as writing vastly better code as well as more compliant code that can help you towards W3C validation, cross browser compatibility and accessibly (especially with issues relating to the Disability Discrimination Act 2005).
I would not class Frontpage 2003 as defunct but I do believe that Microsoft have announced they will no longer support the product in favour of supporting Expression Web instead.
Hope that helps
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