HTML Formatting Instructions - Cascading Style Sheets (CSS)
By default, when you save your document as an HTML file, AbiWord places all formatting instructions into one block at the beginning. These formatting instructions use the Cascading Style Sheet language, and are in the <style> tag in the <head> of your document. From here it is easy to move the styles as a whole (copy and paste) into a new document which can then be externally linked or integrated with your web-site's style sheet.
Bonus points to Paul!