.addtext::after {
    content: "text from CSS! "
}
header,
footer {
    text-align: center;
    font-family: sans-serif;
    padding: 20px;
}

header {
    height: 20%;
    background-color: yellow;
}

footer {
    height: 10%;
    background-color: bisque;
}

main {
    display: flex;
}

#maintext {
    background-color: orange;
    border: 1px solid black;
    width: 50%;
}

aside {
    background-color: lightblue;
    width: 50%;
}

#hover {
    visibility: hidden;
}