In the last month, I've got an increased number of "soft 404" errors reported by Google webmaster tools which actually work well for users.

Configuration (maybe useless):

• I have a website built with rails 3.1
• Authentication is handled by the gem Devise

Problem:

• On this page http://en.bemyboat.com/yacht-charter/9965-sailboat-beneteau-oceanis-43
• Click on "Ask a Boat request" (a simple form, in GET to: http://en.bemyboat.com/boat_requests/new/9965)
• You are redirected with the HTTP status 302 to sign in
• You are then sent back to the new page if successfully sign in.

Google tells me that the link on "ask a boat request" returns a soft 404.

I can't make this form in "POST" (which will solve the problem) because we need to automatically redirect users back to the page after sign in. (the Gem Devise memorizes the "get" link.)

To simplify, the question is: How to protect a private page with authentication, reached with a simple "GET" and not to be penalized by Google as a "soft 404".