Funny thing with text formatting viewed on mobile browsers

[Peter]

I'm stuck with formatting a head line that displays bigger than the body text with mobile browsers (Safari, Chrome). Whatever I do, the head line displays *smaller*, even when I define a style for it.
Test page:
http://www.hoelzenhausen.de/Home_Test/home_test.html

I found a workaround. Placing a dummy text with just a dot in white (before the white background) above the text box makes the text sizes (more) like I want them to appear:
http://www.hoelzenhausen.de/

Any ideas?