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

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

            //Set the popup window to center
            $(id).css('top',  winH/2-$(id).height()/2);
            $(id).css('left', winW/2-$(id).width()/2);

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

        });

        //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();
        });

    });