var current_page = "";

function loadPopup(page){
	var windowWidth = document.documentElement.clientWidth;  
	var windowHeight = document.documentElement.clientHeight;
	var popupHeight;
	var popupWidth;
	
	//if another popup is open close it
	if(current_page != "") closePopup(current_page);
	
	if(page){
		$("#" + page).fadeIn("slow");
		var popupHeight = $("#" + page).height();  
		var popupWidth = $("#" + page).width();
		var x = windowWidth/2-popupWidth/2;
		var y = windowHeight/2-popupHeight/2;
		if(y < 0) y = 0;
		$("#" + page).css({  
			"position": "absolute",  
			"top": y,  
			"left": x
		});
	}
	
	current_page = page;
} 
function closePopup(page){  
	if(page) $("#" + page).fadeOut("slow");
}