function setOpacity( value ) {
 document.getElementById("mypopup_gastenboek").style.opacity = value / 10;
 document.getElementById("mypopup_gastenboek").style.filter = 'alpha(opacity=' + value * 10 + ')';
}

function fadeInMyPopup() {
 for( var i = 0 ; i <= 100 ; i++ )
   setTimeout( 'setOpacity(' + (i / 10) + ')' , 3 * i );
}

function fadeOutMyPopup() {
 for( var i = 0 ; i <= 100 ; i++ ) {
   setTimeout( 'setOpacity(' + (10 - i / 10) + ')' , 3 * i );
 }

 setTimeout('closeMyPopup()', 800 );
}

function closeMyPopup() {
 document.getElementById("mypopup_gastenboek").style.display = "none"
/*ldiv.style.display = 'none';*/
}

function fireMyPopup() {
/*var ldiv = document.getElementById('LoadingDiv');
ldiv.style.display='block';*/
/*Do your ajax calls, sorting or laoding, etc.*/
/*ldiv.style.display = 'none';*/
 setOpacity( 0 );
 myPopupRelocate();
 document.body.onscroll = myPopupRelocate;
 window.onscroll = myPopupRelocate;
 document.getElementById("mypopup_gastenboek").style.display = "block";
 fadeInMyPopup();
  window.setTimeout("closeMyPopup()", 100000);
}

function myPopupRelocate() {
 var scrolledX, scrolledY;
 if( self.pageYOffset ) {
   scrolledX = self.pageXOffset;
   scrolledY = self.pageYOffset;
 } else if( document.documentElement && document.documentElement.scrollTop ) {
   scrolledX = document.documentElement.scrollLeft;
   scrolledY = document.documentElement.scrollTop;
 } else if( document.body ) {
   scrolledX = document.body.scrollLeft;
   scrolledY = document.body.scrollTop;
 }

 var centerX, centerY;
 if( self.innerHeight ) {
   centerX = self.innerWidth;
   centerY = self.innerHeight;
 } else if( document.documentElement && document.documentElement.clientHeight ) {
   centerX = document.documentElement.clientWidth;
   centerY = document.documentElement.clientHeight;
 } else if( document.body ) {
   centerX = document.body.clientWidth;
   centerY = document.body.clientHeight;
 }

// var leftOffset = scrolledX + (centerX - 400) / 2 - 125; //correctie voor vervelende css
 var topOffset = scrolledY + (centerY - 400) / 2 - 100; // correctie voor vervelende css

 document.getElementById("mypopup_gastenboek").style.top = topOffset + "px";
// document.getElementById("mypopup_gastenboek").style.left = leftOffset + "px";
}