Permissions on writable files and folders: /content /include/pri-nav.asp /include pri-nav.js - (add other usual suspects here)
301 redirects from old page to new, pages without equivalent should issue a 404 create a new page via the admin, check it re-writes the nav
Check mobile site
Check styles of sub-pages for all available admin options, i.e. panels, bullet list, next/previous etc.
404 page - check it issues a 404 response, and shows a suitable message
Contact forms - send one to yourself by changing the h_id and also submit one to the client asking for it to be forwarded to you. e.g. "Please forward this message to xxxxxxx@spiderscope.com to confirm its receipt" (don''t skip this!)