$(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();
  });

});