CSS3过渡 – 淡出效果

我试图在纯css中实现“淡出”效果.这是 fiddle
我确实在线查看了几个解决方案.但是在阅读了 documentation online之后 @H_450_3@我试图弄清楚为什么幻灯片动画不起作用.有什么指针吗？

@H_450_3@这是HTML

<div class="dummy-wrap">
    <div class="success-wrap successfully-saved">Saved</div>
</div>

@H_450_3@CSS

.dummy-wrap {
    animation: slideup 2s;
    -moz-animation: slideup 2s;
    -webkit-animation: slideup 2s;
    -o-animation: slideup 2s;
}
.success-wrap {
    width: 75px;
    min-height: 20px;
    clear: both;
    margin-top: 10px;
}
.successfully-saved {
    color: #FFFFFF;
    font-size: 20px;
    padding: 15px 40px;
    margin-bottom: 20px;
    text-align: center;
    -webkit-border-radius: 5px;
    -moz-border-radius: 5px;
    border-radius: 5px;
    BACkground-color: #00b953;
}
@keyframes slideup {
    0% {
        top:0px;
    }
    75% {
        top:0px;
    }
    100% {
        top:-20px;
    }
}
@-moz-keyframes slideup {
    0% {
        top:0px;
    }
    75% {
        top:0px;
    }
    100% {
        top:-20px;
    }
}
@-webkit-keyframes slideup {
    0% {
        top:0px;
    }
    75% {
        top:0px;
    }
    100% {
        top:-20px;
    }
}
@-o-keyframes slideup {
    0% {
        top:0px;
    }
    75% {
        top:0px;
    }
    100% {
        top:-20px;
    }
}

.successfully-saved.hide-opacity{
    opacity: 0;
}

.successfully-saved {
    color: #FFFFFF;
    text-align: center;

    -webkit-transition: opacity 3s ease-in-out;
    -moz-transition: opacity 3s ease-in-out;
    -ms-transition: opacity 3s ease-in-out;
    -o-transition: opacity 3s ease-in-out;
     opacity: 1;
}