Edit in JSFiddle

$(function() {  
    $(".show-on-klik").click(function () { 
    $(".show-elem-rp").toggle("pulsate")
}); 
 });

<div class='rp-tombol-db show-on-klik'>Show Related Post</div>
<div class='show-elem-rp'>
<div id='related-post'>
    javascript related post disini

</div>
</div>

.rp-tombol-db {
  width:70%;
  padding:10px;
  margin:0px auto;
  background-color:#0099cc;
  font-size:16px;
  color:#fff;
  border:1px solid #ddd;
  text-transform:uppercase;
  line-height:40px;
  vertical-align: middle;
  position:relative;
  cursor:pointer;
  text-align:center;
}
.show-elem-rp {display:none;}
#related-post {background:#ccc;width:70%;margin:0px auto;padding:10px}
#related-post h2{font-family:'Oswald', Arial, sans-serif;font-size:16px;color:#4a4a4a;text-transform:uppercase;margin:0 0 15px;padding:0;font-weight:normal}
#related-post a{color:#2c3e50;}
#related-post li{background:url(http://4.bp.blogspot.com/-Bt0JYGRHfpk/T7ZpN5RNSQI/AAAAAAAAGJQ/zQtrWVZwgHA/s1600/bullet.png) no-repeat 1px 5px;color:#2c3e50;text-indent:0;line-height:1.6em;margin:0;padding:0 0 3px 19px}
#related-post a:hover{color:#5295c6;text-decoration:none}
#related-post .widget{margin:0;padding:0}
#related-post ul{list-style:none;margin:0;padding:0}