var xmlhttp    = null;
          var returnCode = null;
          var prevPage   = '1';
          var currPage   = '1';
          function hideContent() {
             for (var I=1; I<8; I++) {
                document.getElementById('content'+I).style.display = 'none';
             }
          }

          function onclickItem(N) {
             prevPage = currPage;
             currPage = N;
             hideContent();
             if (document.all) {
                document.getElementById('content'+N).style.display = 'block';
             }
             else {
                document.getElementById('content'+N).style.display = 'table';
             }
             annuleren();
          }

          function verzenden() {
             var mandatoryFields = [1,2,3,4,9];
             var postVars = ''
             var separator = '';
             document.getElementById('message').innerHTML = '';
             for (var I=0; I <mandatoryFields.length; I++) {
                if (document.forms[0].elements[mandatoryFields[I]].value === '' || document.forms[0].elements[mandatoryFields[I]].value === null) {
                   document.getElementById('message').style.color = 'red';
                   document.getElementById('message').innerHTML = 'Velden voorzien van een (*) invullen, a.u.b.!';
                   return;
                }
             }
             for (var I=0; I <document.forms[0].elements.length; I++) {
                postVars = postVars+separator+'input[]='+document.forms[0].elements[I].value;
                separator = '&';
             }
             loadXHTML('http://www.probol.nl/website/contact.php',postVars,false);
             if (returnCode == 'OK') {
                document.getElementById('message').style.color = '';
                document.getElementById('message').innerHTML = 'Uw verzoek is verzonden, wij nemen zo snel mogelijk contact met u op!';
             }
             else {
                document.getElementById('message').style.color = 'red';
                document.getElementById('message').innerHTML = 'Het verzenden is mislukt! Probeer a.u.b. opnieuw!';
             }
             //alert(returnCode);
          }

          function annuleren() {
             for (var I=0; I <document.forms[0].elements.length; I++) {
                 document.forms[0].elements[I].value = '';
             }
             document.getElementById('message').innerHTML = '';
          }


        function loadXHTML(url,post,async) {
         if (xmlhttp != null) {
            return;
         }

         if (xmlhttp == null) {
            xmlhttp = null;
            if (window.XMLHttpRequest) {
               try {
                  xmlhttp = new XMLHttpRequest();
               }
               catch(e) {
                  xmlhttp = null;
               }
            }
            else {
               if (window.ActiveXObject) {
                  var msxmlobj = [ 'Msxml2.XMLHTTP.3.0','MSXML2.XMLHTTP','Microsoft.XMLHTTP'];
                  for (var i=0; i < msxmlobj.length; i++) {
                     try {
                        xmlhttp = new ActiveXObject(msxmlobj[i]);
                        break;
                     }
                     catch(e){
                       xmlhttp = null;
                     }
                  }
               }
            }
         }
         if (xmlhttp != null) {
            try {
               xmlhttp.open("POST",url,async);
               xmlhttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
               xmlhttp.send(post);
               returnCode = xmlhttp.responseText;
            }
            catch(e) {
               xmlhttp = null;
               returnCode = 'FALSE';
            }
         }
         else {
            alert("Browser does not support XMLHTTP!");
            returnCode = 'FALSE';
         }
      }