<div>Hello!</div>

body{
  background-color: #ddd;
  font-family: arial;
}
div{
  display: block;
  background-color: #fff;
  height: 100px;
  width: 250px;
  margin: 50px auto;
  border-radius: 3px;
  border: solid 1px #ccc;
  position: relative;
  padding: 40px;
  box-sizing: border-box;
}
div:before,
div:after{
  content: '';
  display: inline-block;
  background-color: transparent;
  border: solid 10px transparent; 
  border-top-color: #fff;
  position: absolute;
  bottom: -20px;
  right: 20px;
}
div:before{
  border-width: 11px;
  border-top-color: #ccc;
  bottom: -22px;
}