body {
    height: 100%;
}

#begin_text {
    font-family: Verdana, Geneva, Tahoma, sans-serif;
    text-align: center;
}

.container {
    width: 600px;
    border: 6px solid #000;
    height: 600px;
    margin-left: auto;
    margin-right: auto;
    background-color: red;
    margin-bottom: 50px;
}

.div1 {
    width: 150px;
    background-color: yellow;
    height: 150px;
    float: left;
    border-bottom: 6px solid #000;
    border-right: 6px solid #000;
    box-sizing: border-box;
}

.div2 {
    width: 150px;
    height: 300px;
    background-color: white;
    float: right;
    border-left: 6px solid #000;
    border-bottom: 6px solid #000;
    box-sizing: border-box;
}
.div3 {
    width: 300px;
    height: 150px;
    margin-left: 150px;
    background-color: blue;
    border-bottom: 6px solid #000;
    box-sizing: border-box;
}
.div4 {
    width: 150px;
    height: 300px;
    background-color: white;
    float: left;
    box-sizing: border-box;
    border-right: 6px solid #000;
    border-bottom: 6px solid #000;
}
.div5 {
    width: 150px;
    height: 150px;
    background-color: yellow;
    float: right;
    box-sizing: border-box;
    border-left: 6px solid #000;
    border-bottom: 6px solid #000;
}

.div6 {
    margin-left: 150px;
    width: 150px;
    height: 300px;
    background-color: blue;
    float: right;
    box-sizing: border-box;
    border-left: 6px solid #000;

}
.div7 {
    width: 75px;
    height: 150px;
    float: right;
    background-color: #000000;
    box-sizing: border-box;
    margin-right: 75px;
}
.div8 {
    width: 75px;
    height: 75px;
    background-color: white;
    float: right;
    margin-top: -150px;
    border: 6px solid #000;
    box-sizing: border-box;
    border-left: 3px solid #000;
}
.div9 {
    width: 75px;
    height: 75px;
    background-color: blue;
    float: right;
    margin-top: -75px;
    box-sizing: border-box;
    border-bottom: 6px solid #000;
    border-right: 6px solid #000;
    border-left: 3px solid #000;
}
.div10 {
    width: 300px;
    height: 150px;
    background-color: yellow;
    float: right;
    box-sizing: border-box;
    border-right: 6px solid #000;
}