Background with radius-top inside

Question

Does anyone have an idea how to apply a background (in css) as you can see on the picture attached ?

Thanks

Answer 1

div {
    background:lightgreen;
    width:100%;
    height:200px;
    position:relative;
    text-align:center;
    padding:100px 0 0 0;
    box-sizing:border-box;
}
div:before {
    content:'';
    position:absolute;
    background:white;
    width:100%;
    height:100px;
    top:0;
    left:0;
    border-radius:40%;
    transform:translatey(-50%);
}

<div>div</div>

Answer 2

Something like this?

#wrapper {
    position: relative; /* position:absolute needs a relative parent */
}
#main {
    width: 100px;
    height: 50px;
    background-color: green;
    text-align: center;
}
#cutout {
    width: 100px;
    height: 50px;
    border-radius: 50px / 25px; /* half of width / half of height
                                http://css-tricks.com/the-shapes-of-css/
                                remember to add vendor prefixes if necessary */
    background-color: white;
    position: absolute;
    top: -30px; /* should be -25px, but a little padding looks nicer */
}

<div id='wrapper'>
    <div id='cutout'></div>
    <div id='main'><br>div</div>
</div>

Answer 3

Check the DEMO

<div id="wrapper">
<div id="inner"></div>
</div>


#wrapper {
width: 600px;
height: 300px;    
margin: auto;
margin-top: 50px;
background-color: green;
overflow: hidden;
}

#inner {
width: 1200px;
height: 1200px;
border-radius: 600px;
background-color: #fff;
position: relative;
top: -1100px;
left: -300px;
}