<div id="clouds">
            <div class="cloud x1"></div>
            <div class="cloud x1_5"></div>
            <div class="cloud x2"></div>
            <div class="cloud x3"></div>
            <div class="cloud x4"></div>
            <div class="cloud x5"></div>
        </div>
        <div class='c'>
            <div class='_404'>404</div>
            <hr>
            <div class='_1'>THE PAGE</div>
            <div class='_2'>WAS NOT FOUND</div>
            <a class='btn' href='http://www.laivanduc.com/'>Trang Chủ</a>
        </div>
@import url(https://fonts.googleapis.com/css?family=opensans:500);
body{
                background: #33cc99;
                color:#fff;
                font-family: 'Open Sans', sans-serif;
                max-height:700px;
                overflow: hidden;
            }
            .c{
                text-align: center;
                display: block;
                position: relative;
                width:80%;
                margin:100px auto;
            }
            ._404{
                font-size: 220px;
                position: relative;
                display: inline-block;
                z-index: 2;
                height: 250px;
                letter-spacing: 15px;
            }
            ._1{
                text-align:center;
                display:block;
                position:relative;
                letter-spacing: 12px;
                font-size: 4em;
                line-height: 80%;
            }
            ._2{
                text-align:center;
                display:block;
                position: relative;
                font-size: 20px;
            }
            .text{
                font-size: 70px;
                text-align: center;
                position: relative;
                display: inline-block;
                margin: 19px 0px 0px 0px;
                /* top: 256.301px; */
                z-index: 3;
                width: 100%;
                line-height: 1.2em;
                display: inline-block;
            }
           

            .btn{
                background-color: rgb( 255, 255, 255 );
                position: relative;
                display: inline-block;
                width: 358px;
                padding: 5px;
                z-index: 5;
                font-size: 25px;
                margin:0 auto;
                color:#33cc99;
                text-decoration: none;
                margin-right: 10px
            }
            .right{
                float:right;
                width:60%;
            }
            
            hr{
                padding: 0;
                border: none;
                border-top: 5px solid #fff;
                color: #fff;
                text-align: center;
                margin: 0px auto;
                width: 420px;
                height:10px;
                z-index: -10;
            }
            
            hr:after {
                content: "\2022";
                display: inline-block;
                position: relative;
                top: -0.75em;
                font-size: 2em;
                padding: 0 0.2em;
                background: #33cc99;
            }
            
            .cloud {
                width: 350px; height: 120px;

                background: #FFF;
                background: linear-gradient(top, #FFF 100%);
                background: -webkit-linear-gradient(top, #FFF 100%);
                background: -moz-linear-gradient(top, #FFF 100%);
                background: -ms-linear-gradient(top, #FFF 100%);
                background: -o-linear-gradient(top, #FFF 100%);

                border-radius: 100px;
                -webkit-border-radius: 100px;
                -moz-border-radius: 100px;

                position: absolute;
                margin: 120px auto 20px;
                z-index:-1;
                transition: ease 1s;
            }

            .cloud:after, .cloud:before {
                content: '';
                position: absolute;
                background: #FFF;
                z-index: -1
            }

            .cloud:after {
                width: 100px; height: 100px;
                top: -50px; left: 50px;

                border-radius: 100px;
                -webkit-border-radius: 100px;
                -moz-border-radius: 100px;
            }

            .cloud:before {
                width: 180px; height: 180px;
                top: -90px; right: 50px;

                border-radius: 200px;
                -webkit-border-radius: 200px;
                -moz-border-radius: 200px;
            }
            
            .x1 {
                top:-50px;
                left:100px;
                -webkit-transform: scale(0.3);
                -moz-transform: scale(0.3);
                transform: scale(0.3);
                opacity: 0.9;
                -webkit-animation: moveclouds 15s linear infinite;
                -moz-animation: moveclouds 15s linear infinite;
                -o-animation: moveclouds 15s linear infinite;
            }
            
            .x1_5{
                top:-80px;
                left:250px;
                -webkit-transform: scale(0.3);
                -moz-transform: scale(0.3);
                transform: scale(0.3);
                -webkit-animation: moveclouds 17s linear infinite;
                -moz-animation: moveclouds 17s linear infinite;
                -o-animation: moveclouds 17s linear infinite; 
            }

            .x2 {
                left: 250px;
                top:30px;
                -webkit-transform: scale(0.6);
                -moz-transform: scale(0.6);
                transform: scale(0.6);
                opacity: 0.6; 
                -webkit-animation: moveclouds 25s linear infinite;
                -moz-animation: moveclouds 25s linear infinite;
                -o-animation: moveclouds 25s linear infinite;
            }

            .x3 {
                left: 250px; bottom: -70px;

                -webkit-transform: scale(0.6);
                -moz-transform: scale(0.6);
                transform: scale(0.6);
                opacity: 0.8; 

                -webkit-animation: moveclouds 25s linear infinite;
                -moz-animation: moveclouds 25s linear infinite;
                -o-animation: moveclouds 25s linear infinite;
            }

            .x4 {
                left: 470px; botttom: 20px;

                -webkit-transform: scale(0.75);
                -moz-transform: scale(0.75);
                transform: scale(0.75);
                opacity: 0.75;

                -webkit-animation: moveclouds 18s linear infinite;
                -moz-animation: moveclouds 18s linear infinite;
                -o-animation: moveclouds 18s linear infinite;
            }

            .x5 {
                left: 200px; top: 300px;

                -webkit-transform: scale(0.5);
                -moz-transform: scale(0.5);
                transform: scale(0.5);
                opacity: 0.8; 

                -webkit-animation: moveclouds 20s linear infinite;
                -moz-animation: moveclouds 20s linear infinite;
                -o-animation: moveclouds 20s linear infinite;
            }

            @-webkit-keyframes moveclouds {
                0% {margin-left: 1000px;}
                100% {margin-left: -1000px;}
            }
            @-moz-keyframes moveclouds {
                0% {margin-left: 1000px;}
                100% {margin-left: -1000px;}
            }
            @-o-keyframes moveclouds {
                0% {margin-left: 1000px;}
                100% {margin-left: -1000px;}
            }

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.