If you did this just in a document, it should not affect new documents you
create; the easiest way to return to the defaults for your current document
is to save and close your current document, create a new document, press
Enter a couple of times, then use Insert | File to insert your current
document. You can then delete the empty paragraphs at the beginning. See
also http://word.mvps.org/FAQs/Customization/CustomizeNormalTemplate.htm

If the changes are affecting all new documents, see
http://word.mvps.org/FAQs/AppErrors/BlankDocNotBlank.htm

--
Suzanne S. Barnhill
Microsoft MVP (Word)