CSS3 分类菜单效果如下所述: HTML <html> <head> <title></title> <style type="text/css"> #bg { width: 1270px; height: 751px; margin: 0 auto; background: url("images/bg.jpg") no-repeat; } .sblock { width: 800px; height: 250px; margin: 0 auto;} /*.sbl