function popup() {
  popWidth = 600;

  //Fade in Background
  $('body').append('<div id="fade"></div>'); //Add the fade layer to bottom of the body tag.
  $('#fade').css({'filter' : 'alpha(opacity=30)'}).fadeIn(); //Fade in the fade layer

  //Fade in the Popup and add close button
  $('#popup').fadeIn().css({ 'width': Number( popWidth ) }).prepend('<a href="#" class="close"><img src="/images/close_pop.png" class="btn_close" title="Zamknij" alt="Zamknij" /></a>');

  //Define margin for center alignment (vertical + horizontal) - we add 80 to the height/width to accomodate for the padding + border width defined in the css
  var popMargTop = ($('#popup').height() + 80) / 2;
  var popMargLeft = ($('#popup').width() + 80) / 2;

  //Apply Margin to Popup
  $('#popup').css({
          'margin-top' : -popMargTop,
          'margin-left' : -popMargLeft
  });

  //Close Popups and Fade Layer
  $('a.close, #fade').live('click', function() { //When clicking on the close or fade layer...
    $('#fade , #popup').fadeOut(); //fade them both out
    $('#fade').remove();
    return false;
  });
}