I have an applet started by jnlp/javaws and it generally works well on all combinations of browsers/OS. So the mime type etc. is correct. The only issue is that when using MSIE 9 (and only that) after downloading the jnlp the bar at the lower edge of the browser window appears where you have to click "Open" to start the javaws.
There is no checkbox like "Do this every time from now on"/"Do not ask again" so there is no way round this one extra click every time.
Anyone could provide a hint as to where to go to make this happen without having this extra click every time please?
Additional Info: before the "Open" Option appears, there is something like "security check" (sorry we only have a german MSIE "Sicherheitsüberprüfung wird ausgeführt") in the bottom bar in the browser window.
Colleagues found out: It is (again) the "Smart Screen Filter" in MSIE that is causing the problem, disabling it in the Security Tab/Site Settings in the MSIE Internet options (for the level that the site delivering the jnlp) fixes the issue.