$(document).ready(function() {
    $("#big").dialog(
    {
        modal: true,
        width: 856,
        height: 480,
        autoOpen: false
    });

    $("#gallery div").click(function() {
        var big = $("#big");
        big.dialog('open');
        var url = $(this).find("img").attr("src").replace("t_", "");
        big.find("img")
        .attr("src", "/content/ajax-loader.gif")
        .attr("src", url);
    });
});