why does height and top attribute not work when position is relative?

Question

This will position the box a little below the top

H         


        
                      

              相关标签:
       
      

Answer 1

Your box can't have a height that's a percentage of its parent if its parent doesn't have a fixed height, because then the box wouldn't know how high it needs to be (typically such a parent would be body or some other wrapper element).

As a direct consequence, top with a percentage won't have any effect either.