// JavaScript Document

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 - 250) / 2;
var topOffset = scrolledY + (centerY - 200) / 2;

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

function fireGVwindow() {
myPopupRelocate();
document.getElementById("mypopup").style.display = "block";
document.body.onscroll = myPopupRelocate;
window.onscroll = myPopupRelocate;
}