#wrapper {
width: 500px;
height:400px;
background: transparent;
border: 0;
/* Define half of half semi-cicle on the top for all */
background:
radial-gradient(circle at 0 100%, transparent 0, yellow 0) bottom left,
radial-gradient(circle at 100% 100%, transparent 0, yellow 0) bottom right,
radial-gradient(circle at 0 0, transparent 25%, yellow 15px) top right,
radial-gradient(circle at 100% 0, transparent 25%, yellow 15px) top left;
/*Define top half of half circle background for specific Safari 5.1- 6.0*/
background:
-webkit-radial-gradient(circle at 0 100%, transparent 0, yellow 0) bottom left,
-webkit-radial-gradient(circle at 100% 100%, transparent 0, yellow 0) bottom right,
-webkit-radial-gradient(circle at 0 0, transparent 25%, yellow 15px) top right,
-webkit-radial-gradient(circle at 100% 0, transparent 25%, yellow 15px) top left;
/*Define top half of half circle background for specific Opera 11.6-12.0*/
background:
-o-radial-gradient(circle at 0 100%, transparent 0, yellow 0) bottom left,
-o-radial-gradient(circle at 100% 100%, transparent 0, yellow 0) bottom right,
-o-radial-gradient(circle at 0 0, transparent 25%, yellow 15px) top right,
-o-radial-gradient(circle at 100% 0, transparent 25%, yellow 15px) top left;
/*Define top half of half circle background for specific Firefox 3.6-15*/
background:
-moz-radial-gradient(circle at 0 100%, transparent 0, yellow 0) bottom left,
-moz-radial-gradient(circle at 100% 100%, transparent 0, yellow 0) bottom right,
-moz-radial-gradient(circle at 0 0, transparent 25%, yellow 15px) top right,
-moz-radial-gradient(circle at 100% 0, transparent 25%, yellow 15px) top left;
/*repeat half of half circle*/
background-size: 51% 51%;
background-repeat: no-repeat;
border: 0;
-webkit-box-sizing: border-box;
-moz-box-sizing: border-box;
box-sizing: border-box;
}
#content{
padding-top: 25%;
word-wrap: break-word;
}
<div id="wrapper" class="half-circle">
<div id="content">asdasdasdasdasdasdasdasdasdasdasdasdasdasdsdasdasdasdasdasdasdasdasdasdasdasdasdasdassdasdadasasdasdasdasdasd</div>
</div>