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One reason you might want to add additional content to the Head section of the POST response page would be if you wanted to use something like Google Analytics (GA) to generate statistics about the usage of your Identity Provider, GA can provide the ability to generate useful statistics of how many logins are processed by your IdP, by SP etc. (Just keep in mind that GA will write out various cookies to the user'w s browser, and you probably want to read up about those cookies, how they are used, and what the default lifetime is for each. By including the appropriate directives, you can control the lifetime and usage of those cookies, at least to some extent.)
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