JSFiddle - React, Tailwind, and code Playground

HTML

<div id='cssmenu'>
 <ul>
  <li class='active'><a><span></span></a></li>
  <li class='active'><a><span>RAPORLAR</span></a>
   <ul>
    <li><a rel="sorgulama">Rapor Sorgula</a></li>
    <li><a rel="raporekle">Rapor Ekle</a></li>
   </ul>
  </li>
  <li class='active'><a><span>FORMLAR</span></a>
   <ul>
    <li><a rel="katfoyu">Kat Föyü</a></li>
    <li><a rel="dolapfoy">Dolap Föyü</a></li>
    <li><a rel="yapilanisler">Yapılan İşler</a></li>
   </ul>
  </li>
 </ul>
</div>
<div style="border:0px solid gray;  width:99%; margin-bottom: 0em;  margin-top: 0em;  height:85%">
 <div id="sorgulama" class="sekme">
     <iframe src="http://deneme.com/" target="ana" width="100%" height="100%" ></iframe>
 </div>
 <div id="raporekle" class="sekme">
  <iframe src="ekle.asp" target="ana" width="100%" height="100%" ></iframe>
 </div>
 <div id="katfoyu" class="sekme">
  <iframe src="DOSYALAR/kat_foy.asp" width="100%" height="100%" ></iframe>
 </div>
 <div id="yapilanisler" class="sekme">
  <iframe src="DOSYALAR/yapilan_isler.asp" width="100%" height="100%" ></iframe>
 </div>
 <div id="dolapfoy" class="sekme">
  <iframe src="DOSYALAR/dolap_foy.asp" width="100%" height="100%" ></iframe>
 </div>
</div>

CSS

#cssmenu ul {
  margin: 0;
  padding: 0;
}
#cssmenu li {
  margin: 0;
  padding: 0;
}
#cssmenu a {
  margin: 0;
  padding: 0;
}
#cssmenu ul {
  list-style: none;
}
#cssmenu a {
  text-decoration: none;
}
#cssmenu {
  height: 50px;
  background-color: #232323;
  box-shadow: 0px 2px 3px rgba(0, 0, 0, 0.4);
  width: auto;
}
#cssmenu > ul > li {
  float: left;
  margin-left: 15px;
  position: relative;
}
#cssmenu > ul > li > a {
  color: #a0a0a0;
  font-family: Verdana, 'Lucida Grande';
  font-size: 15px;
  line-height: 50px;
  padding: 15px 20px;
  -webkit-transition: color .15s;
  -moz-transition: color .15s;
  -o-transition: color .15s;
  transition: color .15s;
}
#cssmenu > ul > li > a:hover {
  color: #ffffff;
}
#cssmenu > ul > li > ul {
  opacity: 0;
  visibility: hidden;
  padding: 16px 0 20px 0;
  background-color: #fafafa;
  text-align: left;
  position: absolute;
  top: 35px;
  left: 50%;
  margin-left: -90px;
  width: 180px;
  -webkit-transition: all .3s .1s;
  -moz-transition: all .3s .1s;
  -o-transition: all .3s .1s;
  transition: all .3s .1s;
  -webkit-border-radius: 5px;
  -moz-border-radius: 5px;
  border-radius: 5px;
  -webkit-box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.4);
  -moz-box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.4);
  box-shadow: 0px 1px 3px rgba(0, 0, 0, 0.4);
}
#cssmenu > ul > li:hover > ul {
  opacity: 1;
  top: 45px;
  visibility: visible;
}
#cssmenu > ul > li > ul:before {
  content: '';
  display: block;
  border-color: transparent transparent #fafafa transparent;
  border-style: solid;
  border-width: 10px;
  position: absolute;
  top: -20px;
  left: 50%;
  margin-left: -10px;
}
#cssmenu > ul ul > li {
  position: relative;
}
#cssmenu ul ul a {
  color: #323232;
  font-family: Verdana, 'Lucida Grande';
  font-size: 13px;
  background-color: #fafafa;
  padding: 5px 8px 7px 16px;
  display: block;
  -webkit-transition: background-color 0.1s;
  -moz-transition: background-color 0.1s;
  -o-transition: background-color 0.1s;
  transition:...

JavaScript

$("a").click(function(){
    $('.sekme').css({"display": ''});
    $("#"+$(this).attr("rel")).css({"display": 'block'});
})