html, body {
margin: 0;
padding: 0;
width: 100%;
height: 100%;
}
#main {
width: 50%;
min-height: 50%;
margin: auto;
text-align: center;
background-color: lightgrey;
padding: 1em;
-moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box;
}
#main h1 {
margin: 0;
}
table td, th {
padding: 0.5em;
border: 1px solid black;
}
table {
border-collapse: collapse;
margin: auto;
}