I am creating a website.
I have written the HTML part and now I am writing the stylesheet. But there is always some space above my header. How can I remove it?
To prevent unexpected margins and other browser-specific behavior in the future, I'd recommend to include reset.css in your stylesheets.
Be aware that you'll have to set the h[1..6] font size and weight to make headings look like headings again after that, and many other things.
Try margin-top:
<header style="margin-top: -20px;">
...
Edit:
Now I found relative position probably a better choice:
<header style="position: relative; top: -20px;">
...