jQuery popup okno

<script src="popup.js" type="text/javascript"></script>
<div id="button"><input type="submit" value="Klikni" /></div>
	<div id="popupContact">
		<a id="popupContactClose">x</a>
		<h1>Nadpis</h1>
		<p id="contactArea">
			Text
		</p>
	</div>
	<div id="backgroundPopup"></div>

var popupStatus = 0;
function loadPopup(){
	if(popupStatus==0){
		$("#backgroundPopup").css({
			"opacity": "0.7"
		});
		$("#backgroundPopup").fadeIn("slow");
		$("#popupContact").fadeIn("slow");
		popupStatus = 1;
	}
}

function disablePopup(){
	if(popupStatus==1){
		$("#backgroundPopup").fadeOut("slow");
		$("#popupContact").fadeOut("slow");
		popupStatus = 0;
	}
}


function centerPopup(){
	var windowWidth = document.documentElement.clientWidth;
	var windowHeight = document.documentElement.clientHeight;
	var popupHeight = $("#popupContact").height();
	var popupWidth = $("#popupContact").width();
	$("#popupContact").css({
		"position": "absolute",
		"top": windowHeight/2-popupHeight/2,
		"left": windowWidth/2-popupWidth/2
	});
	//IE6
	$("#backgroundPopup").css({
		"height": windowHeight
	});	
}
$(document).ready(function(){
	
	$("#button").click(function(){
		centerPopup();
		loadPopup();
	});				
	$("#popupContactClose").click(function(){
		disablePopup();
	});
	$("#backgroundPopup").click(function(){
		disablePopup();
	});


});

<div id="button"><input type="submit" value="Klikni" /></div>
<div id="button"><input type="submit" value="Klikni2" /></div>
<div id="button"><input type="submit" value="Klikni3" /></div>