jQuery.fn.loadthumb = function(options) {
    options = $.extend({ src: "" }, options);
    
    var _self = this;
    _self.hide();
    
    _self.attr("src", options.src);
    _self.fadeIn("slow");

    return false;
}

function showImg(index) {
    var src = ["/images/index_banner/01.jpg", "/images/index_banner/02.jpg", "/images/index_banner/03.jpg"];

    $("#banner-img").loadthumb({ src: src[index] });
}

$(function() {
    var ad_index = 0;
    var banner_navs = $("div.banner-nav > ul > li");
    banner_navs.click(function() {
        ad_index = banner_navs.index(this);

        banner_navs.removeClass('on');
        $(this).addClass('on');

        showImg(ad_index);
    });
});