<p>
  <input type="checkbox" name="checkbox-1"><label for="checkbox-1"></label>
  Select Me
</p>

body{
  font-family: sans-serif;
  line-height: 1.3;
  font-size: 0.9em;
  color: #666;
  background: #ececec;
  padding: 4em;
  }

p {
  position: relative;
  }

p > input[type="checkbox"]{
  cursor: pointer;
  position: absolute;
  left: 3px;
  top: 0;
  z-index:2;
  width: 26px;
  height: 26px;
  opacity: 0;
  vertical-align: middle;
  }

p > input[type="checkbox"] +label{
  vertical-align: middle;
  border: 2px solid #ccc;
  background-color: #fff;
  height: 26px;
  width: 26px;
  margin-right: 16px;
  display: inline-block;
  z-index:1;
  position: relative;
  -webkit-border-radius: 50%;
     -moz-border-radius: 50%;
          border-radius: 50%;
  }

p > input[type="checkbox"]:checked+label{
  background: -webkit-gradient(linear, left bottom, left top, color-stop(0, #a40017), color-stop(1, #d2828d));
  background: -moz-linear-gradient(center bottom, #a40017 0%, #d2828d 100%);
  box-shadow: 0 2px 7px rgba(0,0,0, 0.6);
  border: 2px solid #fff;
  }

p > input[type="checkbox"]:checked+label:after {
  content: '\2714';
  text-indent: 0;
  font-size: 15px;
  color: #fff;
  position: absolute;
  top: 4px;
  left: 7px;
  width: 13px;
  text-shadow: 0 -1px 0 rgba(0,0,0, 0.7);
  }