function checkSignupForm() {
   var form = document.forms['lb_register'];
   var lb_fields = new Array('name', 'username', 'email', 'password');
   var lb_titles = new Array('Name', 'Username', 'Email', 'Password');
   var error = '';
   for (var i = 0; i < lb_fields.length; i++) {
      var key = lb_fields[i];
      var value = document.getElementById('lb_' + key).value;
      if ('' == value) {
         error = lb_titles[i];
         break;
      }
   }
   if ('' != error) {
      alert(error + " can't be empty. \n Please fill this field.");
      return false;
   } else {
      if (document.getElementById('lb_password2').value !=  document.getElementById('lb_password').value) {
         alert("Password does not match Retype Password.");
         return false;
      }
   }
   form.submit();
}


function onOpenLoginBox() {
   var overlayDiv = document.getElementById('lb_overlay');
   var boxDiv = document.getElementById('lb_box');
   overlayDiv.style.display = 'block';
   boxDiv.style.display = 'block';
   center(boxDiv);
}

function onCloseLoginBox() {
   var overlayDiv = document.getElementById('lb_overlay');
   var boxDiv = document.getElementById('lb_box');
   overlayDiv.style.display = 'none';
   boxDiv.style.display = 'none';
}

function center(element) {
   var my_width  = 0;
   var my_height = 0;
   var divWidth = 514;
   var divHeight = 314;


   if ( typeof( window.innerWidth ) == 'number' ){
      my_width  = window.innerWidth;
      my_height = window.innerHeight;
   }else if ( document.documentElement &&
   ( document.documentElement.clientWidth ||
   document.documentElement.clientHeight ) ){
      my_width  = document.documentElement.clientWidth;
      my_height = document.documentElement.clientHeight;
   }
   else if ( document.body &&
   ( document.body.clientWidth || document.body.clientHeight ) ){
      my_width  = document.body.clientWidth;
      my_height = document.body.clientHeight;
   }

   element.style.position = 'absolute';
   element.style.zIndex   = 99;

   var scrollY = 0;

   if ( document.documentElement && document.documentElement.scrollTop ){
      scrollY = document.documentElement.scrollTop;
   }else if ( document.body && document.body.scrollTop ){
      scrollY = document.body.scrollTop;
   }else if ( window.pageYOffset ){
      scrollY = window.pageYOffset;
   }else if ( window.scrollY ){
      scrollY = window.scrollY;
   }


   var setX = ( my_width  - divWidth  ) / 2;
   var setY = ( my_height - divHeight ) / 2 + scrollY;

   setX = ( setX < 0 ) ? 0 : setX;
   setY = ( setY < 0 ) ? 0 : setY;

   element.style.left = (setX + 100) + "px";
   element.style.top  = setY + "px";
   element.style.display  = 'block';
   var overlayDiv = document.getElementById('lb_overlay');
   overlayDiv.style.width = my_width + "px";
   overlayDiv.style.height = my_height + "px";
   overlayDiv.style.top = scrollY + "px";
   overlayDiv.style.left = "0px";

}