style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

div {
    border: solid 1px black;
}

.myBlock {
    height: 100vh;
    margin: 0 auto;
    width: 70%;
}

#header {
    text-align: center;
    font-size: 40px;
    width: 100%;
    height: 10%;
    background-color: blue;
}

#header:hover {
    background-color: black;
}

#content-container {
    width: 100%;
    height: 80%;
}

#left_panel {
    float: left;
    height: 100%;
    width: 15%;
    background-color: orangered;
}

#left_panel:hover {
    background-color: black;
}

#content-block {
    float: right;
    height: 100%;
    width: 85%;

}

#content-name {
    width: 100%;
    height: 15%;
    background-color: yellow;
    text-align: center;
    font-size: 40px;
    color: darkred;
}

#content-name:hover {
    background-color: black;
}

#content {
    padding-left: 20px;
    width: 100%;
    height: 85%;
}

#footer {
    width: 100%;
    height: 10%;
    background-color: blue;
}

#footer:hover {
    background-color: black;
}

span {
    font-weight: bold;
    cursor: pointer;
}