* {box-sizing: border-box;}
.header {
    width: 100%;
    border: solid black 5px;
    border-radius: 10px;
    height: 150px;
    text-align: center;
    color: aqua;
    font-size: 40px;
    font-family: "Times New Roman";
    background-color: brown;
}

.left {
    float: left;
    width: 25%;
    border: solid black 5px;
    border-radius:10px;
    height: 1000px;
    color:aqua;
    font-size: 25px;
    font-family: "Times New Roman";
    background-color:burlywood;
}
.ul-a {
    list-style-type:square;
}
.right{
    float: right;
    border: solid black 5px;
    border-radius: 10px;
    width: 25%;
    height: 1000px;
    color:aqua;
    font-size: 25px;
    font-family: "Times New Roman";
    background-color: burlywood;
}
.content{
    float: left;
    border: solid black 5px;
    text-align: center;
    border-radius: 10px;
    width: 50%;
    height:1000px;
    color: aqua;
    font-size: 50px;
    font-family: "Times New Roman";
    background-color:cadetblue;
}
.footer{
    float: bottom;
    border: solid black 5px;
    border-radius: 10px;
    text-align: center;
    color:aqua;
    font-size: 25px;
    font-family: "Times New Roman";
    background-color: brown;
}
.thumbnail {
    height: 150px;
    width:  200px;
    border: 5px solid black;
    border-radius:10px;
    margin: 20px;
    transition: all .5s ease-in-out;
}