var scrollTop = 0;

$(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 height and width to mask to fill up the whole screen   
        $('#mask').css({ 'width': maskWidth, 'height': maskHeight });

        //transition effect        
        $('#mask').fadeIn(1000);
        $('#mask').fadeTo(1500, 0.8);

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

        scrollTop = $(window).scrollTop();
        $(document).scrollTo('50%', 800);

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


    });

    //if close button is clicked   
    $('.window .close').click(function(e) {
        //Cancel the link behavior
        e.preventDefault();
        $(document).scrollTo(scrollTop, 800);
        $('#mask, .window').fadeOut(1000);
    });

    //if mask is clicked   
    $('#mask').click(function() {
        $(document).scrollTo(scrollTop, 800);
        $('#mask, .window').fadeOut(1000);
    });
});