radial-gradient()

* {
 margin: 0;
 padding: 0;
}

.main {
 height: 600px;
 width: 900px;
 position: absolute;
 top: 50%;
 left: 50%;
 margin-top: -300px;
 margin-left: -450px;
}

.top {
 height: 275px;
 width: 900px;
}

.empty {
 height: 50px;
 width: 900px;
}

.bottom {
 height: 275px;
 width: 900px;
}

.wrapper {
 width: 25%;
 height: 100%;
 float: left;
}

#div1, #div2, #div3, #div4, #div5, #div6, #div7, #div8 {
 height: 200px;
 width: 200px;
 float: left;
 position: relative;
 top: 50%;
 left: 50%;
 margin-top: -100px;
 margin-left: -100px;
} 

#div1 {
 background: radial-gradient(circle, #FFF, #000);
 background: -moz-radial-gradient(circle, #FFF, #000);
 background: -o-radial-gradient(circle, #FFF, #000);
 background: -webkit-radial-gradient(circle, #FFF, #000);
 background: -ms-radial-gradient(circle, #FFF, #000);
}



#div4 {
 background: radial-gradient(circle, #FFF 50%, #000 50%);
 background: -moz-radial-gradient(circle, #FFF 50%, #000 50%);
 background: -o-radial-gradient(circle, #FFF 50%, #000 50%);
 background: -webkit-radial-gradient(circle, #FFF 50%, #000 50%);
 background: -ms-radial-gradient(circle, #FFF 50%, #000 50%);
 border-radius: 50%;
}

#div5 {
 background: radial-gradient(right, circle, #FFF 60%, #000 40%);
 background: -moz-radial-gradient(right, circle, #FFF 60%, #000 40%);
 background: -o-radial-gradient(right, circle, #FFF 60%, #000 40%);
 background: -webkit-radial-gradient(right, circle, #FFF 60%, #000 40%);
 background: -ms-radial-gradient(right, circle, #FFF 60%, #000 40%);
 border-radius: 50%;
}

#div6 {
 background: radial-gradient(top, circle, #FFF 60%, #000 40%);
 background: -moz-radial-gradient(top, circle, #FFF 60%, #000 40%);
 background: -o-radial-gradient(top, circle, #FFF 60%, #000 40%);
 background: -webkit-radial-gradient(top, circle, #FFF 60%, #000 40%);
 background: -ms-radial-gradient(top, circle, #FFF 60%, #000 40%);
 border-radius: 50%;
}

#div7 {
 background: radial-gradient(bottom, circle, #FFF 60%, #000 40%);
 background: -moz-radial-gradient(bottom, circle, #FFF 60%, #000 40%);
 background: -o-radial-gradient(bottom, circle, #FFF 60%, #000 40%);
 background: -webkit-radial-gradient(bottom, circle, #FFF 60%, #000 40%);
 background: -ms-radial-gradient(bottom, circle, #FFF 60%, #000 40%);
 border-radius: 50%;
}

#div8 {
 background: radial-gradient(left, circle, #FFF 60%, #000 40%);
 background: -moz-radial-gradient(left, circle, #FFF 60%, #000 40%);
 background: -o-radial-gradient(left, circle, #FFF 60%, #000 40%);
 background: -webkit-radial-gradient(left, circle, #FFF 60%, #000 40%);
 background: -ms-radial-gradient(left, circle, #FFF 60%, #000 40%);
 border-radius: 50%;
}

.letter {
 text-align: center;
 line-height: 200px;
 color: #F00;
 font-size: 68px;
 font-weight: bold;
}