$("#menu_tl").click(function() {

    $('.page').fadeOut();
    $('.page').animate({
        "width":  "0px","height": "0px","top":    "50px","left":   "50px"
    });

    $('#page1').fadeIn();
    $('#page1').animate({
        "width":  "500px","height": "400px","top":    "-350px","left":   "-450px"
    },2000);
});

$("#menu_tr").click(function() {

    $('.page').fadeOut();
    $('.page').animate({
        "width":  "0px","left":   "50px"
    });

    $('#page2').fadeIn();
    $('#page2').animate({
        "width":  "500px","height": "400px"
    },2000);
});

但是我想说的是，当第二个功能被点击时，所有改变的CSS将被重置。这意味着以下行是错误的：

$('.page').animate({
    "width":  "0px","left":   "50px"
});

是错误的，应该被全局重置替换。希望这很清楚