CSS 및 HTML을 사용하여 기본 콘텐츠 div 채우기 화면 높이를 만드는 방법

.mainbody{  
   position: absolute;//here we are setting the position of an element as absolute
   top: 30px; /* here we are defining Header Height to 30 px */
   bottom: 10px; /*here we are defining  Footer Height to 10 px */
   width: 100%;// here we are setting the width to 100%
}