<style>
    div#t {
        width: 400px;
        height: 400px;
        border: double rgba(255,0,0,1);
        border-width: 100px 139px;
        border-radius: 200px / 100px;
        border-left-color: rgba(0,0,255,1);
        -moz-box-sizing: border-box;
        box-sizing: border-box;
        margin: 20px;
    }
</style>
<div id="t"></div>