You may receive one of the following errors on your mobile device
Error: The certificate from the server is not validated.
Error: “This certificate is not from a trusted authority” when attempting to establish a secure connection with Android Mobile phones prior to version 2.2
There are problems with the security certificate for this site
error adding account. certificate from server is not validated
Invalid Server Certificate
From 9th December 2010 RapidSSL and Geotrust certificates have been issued from a new 2048Bit root. The GeoTrust Global CA root is not installed on various mobile devices. The GeoTrust Global CA may be included in a future update of these devices.
Until then you can install the Geotrust Cross Root CA and relevant Intermediate CA.