html {
    height: 100%;
}

body{
    height: 100%;
    margin:0;
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background: #f0f0f0;
    background-size:cover;
    background-attachment:fixed;
}

.container{
    height: 97%;
    display:grid;
    grid-template-columns:200px 1fr 250px;
    grid-template-rows:auto 1fr;
    gap:10px;
    padding:10px;
}

.topmenu{
    grid-column:1 / 4;
}

.left{
    grid-column:1;
}

.center{
    grid-column:2;
}

.right{
    grid-column:3;
}

.box{
    background:white;
    padding:10px;
    border-radius:6px;
}

.footer{
    grid-column:1 / 4;
    text-align: center;
}

.content {
    padding: 20px;
    max-width: 900px;
    margin: auto;
    background: #fff;
    min-height: 500px;
    border-radius: 8px;
    box-shadow: 0 0 10px #ccc;
}