On the Chromium blog, Google mentioned two key changes that come with the latest Google Chrome Frame update. The first is that until now, Chrome Frame has used the <meta> tag for invocation. Due to potential problems , Chrome Frame now also allows sites to serve an HTTP header for invocation. Use of the <meta> tag is still supported, however.
The second change is that the “cf” protocol has been renamed to “gcf” and “gcf” is disabled by default. Google says the change will help avoid misuse of the feature and will reduce the number of spurious compatibility issues.
“You can enable it on your local system for testing by adding a REG_DWORD value named EnableGCFProtocol with a value of 1 to the following registry key: HKCU\Software\Google\ChromeFrame,” says software engineer Alex Russell.
There are more details about the benefits of these changes available in the blog post. Chrome Frame will be automatically updated with the changes.