$( function () {
    setTimeout("$('#top_home').css('background','url(images/header_free_stuff.jpg)')", 3000); 
    setTimeout("$('#top_home').css('background','url(images/header_home.jpg)')", 13000); 
    
    $('.cat_button').hover(function () {
        var img_name = $(this).attr('src');
        img_name = img_name.substring(0,(img_name.length - 4));
        img_name = img_name + '_over.jpg';
        $(this).attr({ src: img_name});
    }, 
    function () {
        var img_name = $(this).attr('src');
        img_name = img_name.substring(0,(img_name.length - 9));
        img_name = img_name + '.jpg';
        $(this).attr({ src: img_name});
    });

});