I created fiddle with header, content and footer.
You can see that CSS for header and footer are analogical. Footer behaves as I want but
header collides with text when scrolling.
Do you know what is wrong?
thank you
As your content div is located after the header, its z-index is "higher" by default, so it will be "on top" of your header when you scroll.
Add
z-index:1000;
to your header css.