function registerEvent() {
    var acomplex = document.getElementById('acomplex').value;
    var aname = document.getElementById('aname').value;
    var cname = document.getElementById('cname').value;
    var noattendees = document.getElementById('noattendees').value;
    var cemail = document.getElementById('cemail').value;
    var cnumber = document.getElementById('cnumber').value;
    var params = "acomplex=" + acomplex + "&aname=" + aname + "&cname=" + cname + "&noattendees=" + noattendees + "&cemail=" + cemail + "&cnumber=" + cnumber;
    var req = new XMLHttpRequest();
    req.open("POST", "send.php", true);
    req.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    req.setRequestHeader("Content-length", params.length);
    req.setRequestHeader("Connection", "close");
    req.onreadystatechange = function() {
       if (req.readyState != 4)  { return; }
       document.getElementById('content').innerHTML = "Thank you for registering. More information will follow in the confirmation email.<a href=\"index.php\">Click here</a> to go back.";
     };
    req.send(params);
}