$(document).ready(function () {

    //Put in the DIV id you want to display
    launchWindow('#dialog1');

    //if close button is clicked
    $('.window #close').click(function () {
        $('#mask').hide();
        $('.window').hide();
    });

    //if mask is clicked
    $('#mask').click(function () {
        $(this).hide();
        $('.window').hide();
    });

});

function launchWindow(id) {

    //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(1000);
    $('#mask').fadeTo("slow", 0.8);

    //Get the window height and width
    var winH = $(window).height();
    var winW = $(window).width();

    var scaleX = (winW / 2) - $(id).width() / 2;
    //Set the popup window to center
    if ($('img', $(id)).length > 0) {

        var $ImgWidth = $('img', $(id)).attr('width');
        if ($ImgWidth > (winW / 2))
            scaleX = (winW / 2) - ($ImgWidth / 2);
    }

    $(id).css('top', winH / 2 - $(id).height());
    $(id).css('left', scaleX);


    //transition effect
    $(id).fadeIn(2000);
}