Get SEO benefit by using Sub-Domains and mod_rewrite
DFF support rewriting URL to add sub-domain (sub-domain is the first portion of the Full Domain name such as www) and also adding more relevant keywords into a particular URL.
These SEO techniques are used to stuff more relevant keyword inside your Web Page URLs.
Go to this link for explanation:
http://www.datafeedfile.com/examples/seo.php?eid=1_0