Symptom:
This is an enhancement request that WebVPN login page should display more intuitive error message in case of a socket timeout. 

The message can be displayed in the following scenario:
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1. Configure ASA for authenticating VPN users with both aaa and certificate.
2. Open a browser and access WebVPN login page.
3. Leave the page untouched for 15 minutes then enter the credential and press login.
4. The authentication fails with "certificate validation error".
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In that condition, ASA is not really validating the certificate and authenticating the user as the socket is no longer valid. Thus the error message should rather indicate something along the lines of "Your connection to the Security Gateway has timed out.  Please re-establish your connection" to avoid confusing the VPN user.

Conditions:
NA