A text-only page, with equivalent information or functionality, shall be provided to make a web site comply with the provisions of these standards, when compliance cannot be accomplished in any other way. The content of the text-only page shall be updated whenever the primary page changes.
 
-- Consistent with WCAG 11.4

When to use text-only pages?  Never! …Well, maybe not never.  Perhaps as a last resort.  Frequently text-only pages are less appealing.  Text-only pages represent segregation.   Text-only pages aren’t updated consistently.  Many websites use text-only site map pages.   In this case, make sure that the text-only link is the first link on the page.   The text-only site must have all the information of the main site, must be updated with the same frequency as the main site, and must be immediately and obviously accessible from the main page.