Problems with forms and IE<10

Problems with forms and IE<10

Hi!

Could it be, that Forms are Broken in IE9 and below? I built a form, jQuery Mobile is built in just for optical reasons, the whole form handlng happens with php. But I can't even sent the form to get to the php-part, because if I click the submit-button the form just hangs with the swirly loading thingy.

If you want to try it by yourself, here's the form:
http://scripts.gewerkschaften-online.at/Y02/vermoegenssteuer/testing.php

(if you don't speak german, you are required to put numbers in every field and hit the button called "berechnen", if the fields are empty, 0 is assumed (but thats part of the php that doesn't start, because it hangs before)).

I tried downgrading JQueryMobile to the legacy versions, but the error stays always the same.

Please help, what am I doing wrong?