I have an <img >-tag in a surrounding DIV container.

<div id="editorCloseBtn">
    <img src="/path/to/image/close_big_grey.png">
</div>

#editorCloseBtn {
  position: absolute;
  top :0;
  right: 0;
  padding: 10px;
  background-color: white;
  border: 4px solid white;
  border-bottom-left-radius: 6px;;
  border-right: none;
  border-top: none;
  cursor: pointer;
}

The Image itself has an height and width of 24 pixels.
The Container has a padding of 10px.
The container gets 4 pixels more height than the content is and I could not figure out why.

I also put the image in a blank body with no CSS and even the body got 4 pixel more height (or lets call it empty space) under the image.