HTML

.chat-box {
  font:normal normal 11px/1.4 Tahoma,Verdana,Sans-Serif;
  color:#333;
  width:200px; /* Chatbox width */
  border:1px solid #344150;
  border-bottom:none;
  background-color:white;
  position:fixed;
  right:10px;
  bottom:0;
  z-index:9999;
  -webkit-box-shadow:1px 1px 5px rgba(0,0,0,.2);
  -moz-box-shadow:1px 1px 5px rgba(0,0,0,.2);
  box-shadow:1px 1px 5px rgba(0,0,0,.2);
}

.chat-box > input[type="checkbox"] {
  display:block;
  margin:0 0;
  padding:0 0;
  position:absolute;
  top:0;
  right:0;
  left:0;
  width:100%;
  height:26px;
  z-index:4;
  cursor:pointer;
  opacity:0;
  filter:alpha(opacity=0);
}

.chat-box > label {
  display:block;
  height:24px;
  line-height:24px;
  background-color:#344150;
  color:white;
  font-weight:bold;
  padding:0 1em 1px;
}

.chat-box > label:before {content:attr(data-collapsed)}

.chat-box .chat-box-content {
  /* padding:10px; */
  display:none;
}

/* hover state */
.chat-box > input[type="checkbox"]:hover + label {background-color:#404D5A}

/* checked state */
.chat-box > input[type="checkbox"]:checked + label {background-color:#212A35}
.chat-box > input[type="checkbox"]:checked + label:before {content:attr(data-expanded)}
.chat-box > input[type="checkbox"]:checked ~ .chat-box-content {display:block}

HTML

<div class="chat-box">
    <input type="checkbox">
    <label data-expanded="Close Chatbox" data-collapsed="Open Chatbox"></label>
    <div class="chat-box-content">

        <!-- Kode buku tamu dsb... -->

    </div>
</div>