A pop-up is a child of the parent window, but it is not a child of the parent DOCUMENT. It is its own independent browser window and is not contained by the parent.
Use an absolutely-positioned DIV and a translucent overlay instead.
EDIT - example
You need jQuery for this:
<style>
html, body {
height:100%
}
#overlay {
position:absolute;
z-index:10;
width:100%;
height:100%;
top:0;
left:0;
background-color:#f00;
filter:alpha(opacity=10);
-moz-opacity:0.1;
opacity:0.1;
cursor:pointer;
}
.dialog {
position:absolute;
border:2px solid #3366CC;
width:250px;
height:120px;
background-color:#ffffff;
z-index:12;
}
</style>
<script type="text/javascript">
$(document).ready(function() { init() })
function init() {
$('#overlay').click(function() { closeDialog(); })
}
function openDialog(element) {
//this is the general dialog handler.
//pass the element name and this will copy
//the contents of the element to the dialog box
$('#overlay').css('height', $(document.body).height() + 'px')
$('#overlay').show()
$('#dialog').html($(element).html())
centerMe('#dialog')
$('#dialog').show();
}
function closeDialog() {
$('#overlay').hide();
$('#dialog').hide().html('');
}
function centerMe(element) {
//pass element name to be centered on screen
var pWidth = $(window).width();
var pTop = $(window).scrollTop()
var eWidth = $(element).width()
var height = $(element).height()
$(element).css('top', '130px')
//$(element).css('top',pTop+100+'px')
$(element).css('left', parseInt((pWidth / 2) - (eWidth / 2)) + 'px')
}
</script>
<a href="javascript:;//close me" onclick="openDialog($('#content'))">show dialog A</a>
<a href="javascript:;//close me" onclick="openDialog($('#contentB'))">show dialog B</a>
<div id="dialog" class="dialog" style="display:none"></div>
<div id="overlay" style="display:none"></div>
<div id="content" style="display:none">
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin nisl felis, placerat in sollicitudin quis, hendrerit vitae diam. Nunc ornare iaculis urna.
</div>
<div id="contentB" style="display:none">
Moooo mooo moo moo moo!!!
</div>