<!--SCRPIT TIL AT OPDAGE EVENTUELL SCROLLED-->

function showdeadcenterdiv(Xwidth,Yheight,divid) {
// First, determine how much the visitor has scrolled

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;
}

// Next, determine the coordinates of the center of browser's window

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;
}

// Xwidth is the width of the div, Yheight is the height of the
// div passed as arguments to the function:
var leftOffset = scrolledX + (centerX - Xwidth) / 2;
var topOffset = scrolledY + (centerY - Yheight) / 2;
// The initial width and height of the div can be set in the
// style sheet with display:none; divid is passed as an argument to // the function
var o=document.getElementById(divid);
var r=o.style;
r.position='absolute';
r.top = topOffset + 'px';
r.left = leftOffset + 'px';
r.display = "block";
} 


<!--SCRPIT TIL MODAL WINDOW-->

$(document).ready(function() {	

	//select all the a tag with name equal to modal
	$('a[name=modal]').click(function(e) {
		//Cancel the link behavior
		e.preventDefault();
		
		//Get the A tag
		var id = $(this).attr('href');
	
		//Get the screen height and width
		var maskHeight = $(document).height();
		var maskWidth = $(window).width();
	
		//Set heigth and width to mask to fill up the whole screen
		$('#mask').css({'width':maskWidth,'height':maskHeight});
		
		//transition effect		
		$('#mask').fadeIn(5);	
		$('#mask').fadeTo("slow",1);
		
		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;
		}
	
	
		//Get the window height and width
		var winH = $(window).height();
		var winW = $(window).width();
		              
		//Set the popup window to center
		$(id).css('top',  (winH/2)+scrolledY-$(id).height()/2);
		$(id).css('left', winW/2-$(id).width()/2);
	
		//transition effect
		$(id).fadeIn(5); 
	
	});
	
	//if close button is clicked
	$('.window .close').click(function (e) {
		//Cancel the link behavior
		e.preventDefault();
		
		$('#mask').hide();
		$('.window').hide();
	});		
	
	//if mask is clicked
	$('#mask').click(function () {
		$(this).hide();
		$('.window').hide();
	});				
});