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Using either http://www.my-site.domain.com or http://my-site.domain.com for OpenID urls works and so does https://www.my-site.domain.com when I enter it for my OpenId url, but I get an error when I enter https://my-site.domain.com. Why?

This plugin (by way of the included SimpleOpenID class) uses cURL to communicate between the plugin and the site hosting the OpenID server. Behind the scenes, there have been some decisions made about how cURL operates in certain situations. When cURL goes to a secure site (one that begins with the protocol https://) cURL has to decide if the url is valid, so cURL, at the least, looks at the site's server's secure certificate and compares the information found on it to the entered url. If these match, cURL decides thing are okay and the communication continues. In this situation, https://www.my-site.domain.com is NOT the same as https://my-site.domain.com. If the site's server's secure certificate has been set up as https://www.my-site.domain.com, cURL will use that as the 'valid' url and reject using other urls, for your safety. Additionally, cURL can complain and fuss a bit if the secure server's certificate is expired.