I have read so many questions and answers on this but none of them seem to fix my problem. Basically I have an HTML and CSS slideshow and I am trying to center this slideshow. I have position: absolute in the code, however when I try to remove that, the images are no longer in a slideshow and are just all down the page. 
Here is my code:
<body>
<div class="container">
    <img src=>
    <img src=>
    <img src=>
    <img src=>
    <img src=>
    <img src=>
    <img src=>
    <img src=>
</div>
<style>
.container {
    position:relative;
}
.container img {
    position:absolute;
    width:900px;
    height:500px
}
@-webkit-keyframes xfade {
    0% {
        opacity: 1;
    }
    12.5% {
        opacity:1;
    }
    16.5% {
        opacity:0;
    }
    96% {
        opacity:0;
    }
    100% {
        opacity:1;
    }
}
@keyframes xfade {
    0% {
        opacity: 1;
    }
    12.5% {
        opacity:1;
    }
    16.5% {
        opacity:0;
    }
    96% {
        opacity:0;
    }
    100% {
        opacity:1;
    }
}
.container img:nth-child(8) {
    -webkit-animation: xfade 120s 0s infinite;
    animation: xfade 120s 0s infinite;
}
.container img:nth-child(7) {
    -webkit-animation: xfade 120s 15s infinite;
    animation: xfade 120s 15s infinite;
}
.container img:nth-child(6) {
    -webkit-animation: xfade 120s 30s infinite;
    animation: xfade 120s 30s infinite;
}
.container img:nth-child(5) {
    -webkit-animation: xfade 120s 45s infinite;
    animation: xfade 120s 45s infinite;
}
.container img:nth-child(4) {
    -webkit-animation: xfade 120s 60s infinite;
    animation: xfade 120s 60s infinite;
}
.container img:nth-child(3) {
    -webkit-animation: xfade 120s 75s infinite;
    animation: xfade 120s 75s infinite;
}
.container img:nth-child(2) {
    -webkit-animation: xfade 120s 90s infinite;
    animation: xfade 120s 90s infinite;
}
.container img:nth-child(1) {
    -webkit-animation: xfade 120s 105s infinite;
    animation: xfade 120s 105s infinite;
}
.container {
    margin: 0 auto;
}
</style>
 
    