A complete list of all changes can be found on Release History page: https://www.telerik.com/support/whats-new/aspnet-ajax/release-history
The script that generates the Facebook standard buttons has been updated to version 2.1. You must add the following XML namespace to the
<html> tag of your document in order for the buttons to work properly in earlier versions of Internet Explorer.
<html xmlns="https://www.w3.org/1999/xhtml" xmlns:fb="http://ogp.me/ns/fb#">
For versions prior to the Q3 2014 release, you must use the following XML namespace:
<html xmlns="https://www.w3.org/1999/xhtml" xmlns:fb="http://www.facebook.com/2008/fbml" xmlns:og="http://opengraphprotocol.org/schema/">
More information on the Facebook platform versioning is available on the official Facebook site: https://developers.facebook.com/docs/apps/versions.
Facebook buttons are not rendered in Internet Explorer 7 because Facebook is phasing out the support for Internet Explorer 7. More information on the matter is available in the Facebook Specifics help article, in the section called "Facebook buttons are not rendered in Internet Explorer 7" .