How can I remove space (margin) above HTML header?

Question

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?

Answer 1

Just for completeness, changing overflow to auto/hidden should do the trick too.

body {
  margin: 0px;
  padding: 0px;
}

header {
  margin: 0px;
  padding: 0px;
  height: 20em;
  background-color: #C0C0C0;
  overflow: auto;
}

  
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