body default margin code example

Example 1: why there's a default margin in html

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

Example 2: css my body have margin top

You probably have an element with margin-top as one of the first children of body.

Read up on collapsing margins.

Purely as a simple test, set padding: 1px on body. If the gap goes away, I'm right.

/* 
from stackoverflow.com ->
css & html5: why does my body have a spacing at the top

 */