I hope i'm on the right site for my problem.
I have an IIS which is hosting an Site which has Windows Authentication enabled. There is only Windows Authentication enabled and nothing else.
When i'm trying to go on the site with any other Browser. IE11, Chrome or Firefox the SSO works as expected.
But when i'm opening the website with the IE9 the credentials are not passed through. They are only passed through when I open the Developer Console in IE 9 F12 and then hit F5.