style.css

body { font-family: Verdana; font-size: 12px; }
#frequency { color: blue; font-weight: bold; display: inline-block; width: 100px; text-align: center; }
#slider { display: inline-block; width: 500px; margin: 0 0 0 15px; }
.label { margin: 0 5px 0 5px; font-weight: bold; color: #333; }
button { 
  -webkit-border-radius: 5px;
  border-radius: 5px;
  font-weight: bold;
  padding: 15px; 
  cursor: pointer; 
  border: 1px solid #ccc; 
  color: black;
  background: #e2e2e2; /* Old browsers */
  background: -moz-linear-gradient(top,  #e2e2e2 0%, #dbdbdb 50%, #d1d1d1 51%, #fefefe 100%); /* FF3.6+ */
  background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#e2e2e2), color-stop(50%,#dbdbdb), color-stop(51%,#d1d1d1), color-stop(100%,#fefefe)); /* Chrome,Safari4+ */
  background: -webkit-linear-gradient(top,  #e2e2e2 0%,#dbdbdb 50%,#d1d1d1 51%,#fefefe 100%); /* Chrome10+,Safari5.1+ */
  background: -o-linear-gradient(top,  #e2e2e2 0%,#dbdbdb 50%,#d1d1d1 51%,#fefefe 100%); /* Opera 11.10+ */
  background: -ms-linear-gradient(top,  #e2e2e2 0%,#dbdbdb 50%,#d1d1d1 51%,#fefefe 100%); /* IE10+ */
  background: linear-gradient(to bottom,  #e2e2e2 0%,#dbdbdb 50%,#d1d1d1 51%,#fefefe 100%); /* W3C */
  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#e2e2e2', endColorstr='#fefefe',GradientType=0 ); /* IE6-9 */
}
button.active { 
  color: white; 
  background: #9dd53a; /* Old browsers */
  background: -moz-linear-gradient(top,  #9dd53a 0%, #a1d54f 50%, #80c217 51%, #7cbc0a 100%); /* FF3.6+ */
  background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#9dd53a), color-stop(50%,#a1d54f), color-stop(51%,#80c217), color-stop(100%,#7cbc0a)); /* Chrome,Safari4+ */
  background: -webkit-linear-gradient(top,  #9dd53a 0%,#a1d54f 50%,#80c217 51%,#7cbc0a 100%); /* Chrome10+,Safari5.1+ */
  background: -o-linear-gradient(top,  #9dd53a 0%,#a1d54f 50%,#80c217 51%,#7cbc0a 100%); /* Opera 11.10+ */
  background: -ms-linear-gradient(top,  #9dd53a 0%,#a1d54f 50%,#80c217 51%,#7cbc0a 100%); /* IE10+ */
  background: linear-gradient(to bottom,  #9dd53a 0%,#a1d54f 50%,#80c217 51%,#7cbc0a 100%); /* W3C */
  filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#9dd53a', endColorstr='#7cbc0a',GradientType=0 ); /* IE6-9 */

}
button:hover { opacity: 0.8; }