Hi David,
Thanks for your suggestion. I have tried this css before. The outcome is:
Background is indeed transparent, but header still contains a shadow even though Header Shadow setting is OFF. As you scroll down the page over different sections and images it is still visible there is a header shadow. Also, the original issue is not resolved where header “blinks” white background as you scroll the page. What I mean is that on load the header is transparent, but when I scroll the page white background appears and header becomes transparent again, when I stop scrolling.
Can it be fixed somehow?
Many thanks
Marek