* {
 margin: 0;
 padding: 0;
}

html {
 height: 100%;
 width: 100%;
}

#header,
#footer {
 width: 100%;
 height: 200px;
 background-color: yellowgreen;
 padding: 5px;
}

#navbar {
 width: 100%;
 height: 50px;
 background-color: tomato;
 padding: 5px;
 position: sticky;
 top: 0;
}

#box {
 width: 100%;
 padding: 10px;
}

#navbar ul li {
 display: inline-block;
 list-style: none;
 padding: 10px;
 line-height: 30px;
 color: white;
}