CofC Web Accessibility Guidelines- Rule (K)

(k) A text-only page, with equivalent information or functionality, shall be provided to make a web site comply with the provisions of this part, when compliance cannot be accomplished in any other way. The content of the text-only page shall be updated whenever the primary page changes.

Translation: If for some reason you cannot provide a Section 508 compliant page (or site), then you must provide a text-only version that contains all the same information. The main site should provide a link to the text site. This alternate version should be updated whenever the main site is changed.

Maintaining a second site makes the Webmaster's job harder, since he has to deal with duplicate pages. A duplicate text-only site should be considered a last resort.