SSA has been using @tabindex=0 to make instructional text on forms focusable for a while.
Their guidance is available from here:
http://www.ssa.gov/oag/acq/oagacq_508.htm
SSA's Guide to Applying Section 508 Standards:
http://www.ssa.gov/oag/info/SSA's%20Guide%20to%20Applying%20Section%20508%20Standards.pdf
The relevant bit is on page 49 in relation to testing against 1194.22(n).
The simplest example I could find of @tabindex is their change of address form:
https://secure.ssa.gov/apps6z/ICOA/main.html
You have to select the OK button to get the actual form. @tabindex=0 is set on a DIV and a couple SPANs.
-----Original Message-----
From: Loretta Guarino Reid [mailto:lorettaguarino@google.com]
Sent: Thu 9/1/2011 5:19 PM
To: Bailey, Bruce
Cc: adam solomon; David MacDonald
Subject: Tabindex on instructions
This is the reminder email to send a pointer to your pages with focusable
instructions.