Answers for "create a cirlce with border 10px"

css rounded corners

/* Set rounded corners with border-radius property */

.class {
  border-radius: 4px;
}

.circle {
  border-radius: 50%;
}

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>