main, body, footer, aside, header{
    font-family: Tahoma, sans-serif;
    font-size: 14px;
    color: black;
    padding: 20px;
    border: 3px solid teal;
    margin: 5px;
    background-color: #f0f0f0;
}

body {
    overflow: auto;
}

aside {
    width: 20%;
    height: 350px;
    position: relative;
    float: left;
    background-color: white;
}

main { 
    width: 70%;
    position: relative;
    float: left;
    padding: 5px;
    background-color: white;
}

#nav_menu {
    overflow: auto;
}

#nav_menu ul { 
    list-style-type: none;
    margin: 0;  
}

#nav_menu ul li { 
    float: left; 
}
#nav_menu ul li a {
    display: block;
    text-align: center;
    width: 180px;
    padding: 1cqh 0;
    text-decoration: none;
    font-weight: bold;
    background-color: #fefefe;
    border: 2px solid black;
    padding: 10px;
}

#nav_menu ul li a:hover {
    background-color: rgb(2, 195, 195);
    color: white;
}

header {
    border: 5px solid teal;
    background-color: white;
}

footer {
    clear: both;
    text-align: center;
    padding: 1em 0;
    background-color: white;
    border: 5px solid teal;
}

a {
    color: black;
    text-decoration: none;
}


h1, h2 {
    text-shadow: 1px grey;
}