title: css: how to center box div element directly in center?
body: <p>when i use top:50% and left:50%</p>
  
  <p>the box is not directly in center. of course when the box is very small, it appears to be centered. but when box is a bit big, it looks as if it's not centered.</p>
  
  <p>how can i resolve this ?</p>