title: Modal pop up displays at the center only when the scrollbar is at the top
body: <p>I am using modal popup, it is not displayed at the center irrespective of whether the scrollbar is at the top or at the bottom. I always want it to be rendered at the center so that user has need not scroll to see that modal pop up. Following is the code i am using :</p>
  
  <p>CSS:</p>
  
  <pre><code>table {
      border-collapse:separate;
      border-spacing:0pt;
  }
  
  caption, th, td {
      font-weight:normal;
      text-align:left;
  }
  
  blockquote:before, blockquote:after, q:before, q:after {
      content:"";
  }
  
  blockquote, q {
      quotes:"" "";
  }
  
  a {
      cursor: pointer;
      text-decoration:none;
  }
  
  br.both {
      clear:both;
  }
  
  #backgroundPopup {
      display:none;
      position:fixed;
      _position:absolute; /* hack for internet explorer 6*/
      height:100%;
      width:100%;
      top:0;
      left:0;
      background:#000000;
      border:1px solid #cecece;
      z-index:1;
  }
  
  #popupContact {
      display:none;
      position:fixed;
      _position:absolute; /* hack for internet explorer 6*/
      height:384px;
      width:408px;
      background:#FFFFFF;
      border:2px solid #cecece;
      z-index:2;
      padding:12px;
      font-size:13px;
  }
  
  #popupContact h1 {
      text-align:left;
      color:#6FA5FD;
      font-size:22px;
      font-weight:700;
      border-bottom:1px dotted #D3D3D3;
      padding-bottom:2px;
      margin-bottom:20px;
  }
  
  #popupContactClose {
      font-size:14px;
      line-height:14px;
      right:6px;
      top:4px;
      position:absolute;
      color:#6fa5fd;
      font-weight:700;
      display:block;
  }
  
  #button {
      text-align:center;
      margin:100px;
  }
  </code></pre>
  
  <p>JavaScript:</p>
  
  <pre><code>//SETTING UP OUR POPUP
  //0 means disabled; 1 means enabled;
  var popupStatus = 0;
  
  //loading popup with jQuery magic!
  function loadPopup(){
      //loads popup only if it is disabled
      if(popupStatus==0){
          $("#backgroundPopup").css({
              "opacity": "0.7"
          });
          $("#backgroundPopup").fadeIn("slow");
          $("#popupContact").fadeIn("slow");
          popupStatus = 1;
      }
  }
  
  //disabling popup with jQuery magic!
  function disablePopup(){
      //disables popup only if it is enabled
      if(popupStatus==1){
          $("#backgroundPopup").fadeOut("slow");
          $("#popupContact").fadeOut("slow");
          popupStatus = 0;
      }
  }
  
  //centering popup
  function centerPopup(){
      //request data for centering
      var windowWidth = document.documentElement.clientWidth;
      var windowHeight = document.documentElement.clientHeight;
      var popupHeight = $("#popupContact").height();
      var popupWidth = $("#popupContact").width();
      //centering
      $("#popupContact").css({
          "position": "absolute",
          "top": windowHeight/2-popupHeight/2,
          "left": windowWidth/2-popupWidth/2
      });
      //only need force for IE6
  
      $("#backgroundPopup").css({
          "height": windowHeight
      });
  
  }
  
  
  //CONTROLLING EVENTS IN jQuery
  $(document).ready(function(){
  
      //LOADING POPUP
      //Click the button event!
  
  
      $(document.body).on('click', '.flag_icons' ,function(e){
      //$('.flag_icon').click(function(){
          //centering with css
          centerPopup();
          //load popup
          loadPopup();
      });
  
      //CLOSING POPUP
      //Click the x event!
      $("#popupContactClose").click(function(){
          disablePopup();
      });
      //Click out event!
      $("#backgroundPopup").click(function(){
          disablePopup();
      });
      //Press Escape event!
      $(document).keypress(function(e){
          if(e.keyCode==27 &amp;&amp; popupStatus==1){
              disablePopup();
          }
      });
  });
  </code></pre>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div id="popupContact"&gt;
          &lt;a id="popupContactClose"&gt;x&lt;/a&gt;
          &lt;h1&gt; Modal Popup Rendered &lt;/h1&gt;
          &lt;p id="contactArea"&gt;
           &lt;/form&gt;
          &lt;/p&gt;
  &lt;/div&gt;
  &lt;div id="backgroundPopup"&gt;&lt;/div&gt;
  </code></pre>