If you are using the Linked Data Theatre and want to access a secure (https) endpoint, in some cases the certificate is not trusted (for example: self-signed certificates, or certificates has no chain to a trusted ROOT certificate in the default Java keystore).
The Linked Data Theatre is capable of trusting certificates in its own keystore, via the SSL functionality of Orbeon. (see: http://doc.orbeon.com/configuration/properties/index.html and http://wiki.orbeon.com/forms/how-to/use-ssl-https)
Go to the https website and export the certificate (most browsers have the option to export a certificate without trusting it). You should end up with a .crt file.
Import the certificate into a newly created keystore (you will be prompted to specify the password for the keystore):
"%JAVA_HOME%/bin/keytool" -import -alias {CERTIFICATE-ALIAS} -keystore ldt.jks -file {CERTIFICATE-FILENAME}
Replace {CERTIFICATE-FILENAME} with the name of the exported certificate file. Choose a name for {CERTIFICATE-ALIAS} that is unique in this keystore for the certificate. Move the keystore file ldt.jks to the \WEB-INF\resources\config directory.
Create the file properties-local.xml in the directory \WEB-INF\resources\config. This file should look something like:
<properties xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:oxf="http://www.orbeon.com/oxf/processors">
<property as="xs:string" name="oxf.http.ssl.hostname-verifier" value="allow-all"/>
<property as="xs:anyURI" name="oxf.http.ssl.keystore.uri" value="file:/{TOMCAT-DIR}/webapps/ROOT/WEB-INF/resources/config/ldt.jks"/>
<property as="xs:string" name="oxf.http.ssl.keystore.password" value="{PASSWORD}"/>
</properties>
Replace {TOMCAT-DIR} with the path to the tomcat directory (including drive letter on windows). Replace {PASSWORD} with the password of the keystore.
Remember to restart the server after you have made the changes.