stylesheet.css

.btn {
  background: #0099ff;
  background-image: -webkit-linear-gradient(top, #0099ff, #00ff26);
  background-image: -moz-linear-gradient(top, #0099ff, #00ff26);
  background-image: -ms-linear-gradient(top, #0099ff, #00ff26);
  background-image: -o-linear-gradient(top, #0099ff, #00ff26);
  background-image: linear-gradient(to bottom, #0099ff, #00ff26);
  -webkit-border-radius: 11;
  -moz-border-radius: 11;
  border-radius: 11px;
  text-shadow: 1px 1px 3px #666666;
  font-family: Arial;
  color: #ffffff;
  font-size: 20px;
  padding: 10px 20px 10px 20px;
  text-decoration: none;
}

.btn:hover {
  background: #60acdb;
  background-image: -webkit-linear-gradient(top, #60acdb, #88d971);
  background-image: -moz-linear-gradient(top, #60acdb, #88d971);
  background-image: -ms-linear-gradient(top, #60acdb, #88d971);
  background-image: -o-linear-gradient(top, #60acdb, #88d971);
  background-image: linear-gradient(to bottom, #60acdb, #88d971);
  text-decoration: none;
}

.center_div{
    margin: 0 auto;
    width:0% /* value of your choice which suits your alignment */

}

.margin-10{margin: 10px;}