// wrap as a jQuery plugin and pass jQuery in to our anoymous function
(function ($) {
    $.fn.cross = function (options) {
        return this.each(function (i) {
            // cache the copy of jQuery(this) - the start image
            var $$ = $(this);

            // get the target from the backgroundImage + regexp
            var target = $$.css('backgroundImage').replace(/^url|[\(\)'"]/g, '');

            // nice long chain: wrap img element in span
            $$.wrap('<span style="position: relative;"></span>')
            // change selector to parent - i.e. newly created span
                    .parent()
            // prepend a new image inside the span
                    .prepend('<img>')
            // change the selector to the newly created image
                    .find(':first-child')
            // set the image to the target
                    .attr('src', target);

            // the CSS styling of the start image needs to be handled
            // differently for different browsers
            if ($.browser.msie) {
                $$.css({
                    'position': 'absolute',
                    'left': 0,
                    'background': '',
                    'top': $(this).offsetTop
                });
            } else if ($.browser.mozilla) {
                $$.css({
                    'position': 'absolute',
                    'left': 0,
                    'background': '',
                    'top': this.offsetTop
                });
            } else if ($.browser.opera && $.browser.version < 9.5) {
                // Browser sniffing is bad - however opera < 9.5 has a render bug 
                // so this is required to get around it we can't apply the 'top' : 0 
                // separately because Mozilla strips the style set originally somehow...                    
                $$.css({
                    'position': 'absolute',
                    'left': 0,
                    'background': '',
                    'top': "0"
                });
            } else { // Safari
                $$.css({
                    'position': 'absolute',
                    'left': 0,
                    'background': ''
                });
            }

            var f;
            f = function (s) {
                $$.animate({ opacity: s }, 5000, function () {
                    if (s == 0) {
                        setTimeout('f(1)', 10000);
                    } else {
                        setTimeout('f(0)', 10000);
                    }
                });
            }

            var z = function () {
                $$.animate({ opacity: 0 }, 5000).delay(5000).animate({ opacity: 1 }, 5000, z).delay(5000);
            }

            z();
        });
    };

})(jQuery);

// note that this uses the .bind('load') on the window object, rather than $(document).ready() 
// because .ready() fires before the images have loaded, but we need to fire *after* because
// our code relies on the dimensions of the images already in place.
$(window).bind('load', function () {
    $('#img_fade').cross();
});