var marginLeft;
var marginTop;
//additional properties for jQuery object
$(document).ready(function () {
    //align element in the middle of the screen
    $.fn.alignCenter = function () {
        if (marginLeft == null) {
            //get margin left
            marginLeft = -$(this).width() + 150 / 2 + 'px';
        }
        if (marginTop == null) {
            //get margin top
            marginTop = -$(this).height() / 2 + 'px';
        }
        //return updated element
        return $(this).css({ 'margin-left': marginLeft, 'margin-top': marginTop });
    };

    $.fn.togglePopup = function () {
        //detect whether popup is visible or not
        if ($('#popup').hasClass('hidden')) {
            //hidden - then display
            //when IE - fade immediately
            if ($.browser.msie) {
                $('#opaco').height($(document).height()).toggleClass('hidden')
                    .click(function () { $(this).togglePopup(); });
            }
            else
            //in all the rest browsers - fade slowly
            {
                $('#opaco').height($(document).height()).toggleClass('hidden').fadeTo('slow', 0.7)
                    .click(function () { $(this).togglePopup(); });
            }

            $('#popup')
         .html($(this).html())
         .alignCenter()
         .toggleClass('hidden');
        }
        else {
            //visible - then hide
            $('#opaco').toggleClass('hidden').removeAttr('style').unbind('click');
            $('#popup').toggleClass('hidden');
        }
    };
});