create circle and curve in html code example

Example 1: css circle border

.circle {
    background-color:#fff;
    border:1px solid red;    
    height:100px;
    border-radius:50%;
    -moz-border-radius:50%;
    -webkit-border-radius:50%;
    width:100px;
}
<div class="circle"></div>

Example 2: css button style rectangle

<div class="placeholder-box">
  <button type="button"> Button Text Here </button>
  <p>Nunc condimentum mauris elit</p>
  <ul>
    <li>Duis quis eros felis</li>
    <li>Nulla facilisi</li>
  </ul>
</div>