html

 <div class="heart"></div>

css3

 <style>
        *{
            padding: 0;
            margin: 0;

        }
           .heart {
    animation:heartbeat 1s infinite;
    -webkit-animation:heartbeat 1s infinite;
    /* Safari 和 Chrome */

        width:198px;
    height:198px;
    background:#f00;
    position:relative;
    filter:drop-shadow(0px 0px 20px rgb(255,20,20));
    transform:rotate(45deg);
    left:200px;
    top:50px;
}
.heart:before,.heart:after {
    content:"";
    position:absolute;
    width:200px;
    height:200px;
    background:#f00;
    border-radius:100px;
}
.heart:before {
    left:-100px;
}
.heart:after {
    left:0;
    top:-100px;
}
@keyframes heartbeat {
    0% {
    transform:rotate(45deg) scale(0.8,0.8);
    opacity:1;
}
25% {
    transform:rotate(45deg) scale(1,1);
    opacity:0.8;
}
100% {
    transform:rotate(45deg) scale(0.8,0.8);
    opacity:1;
}
}
    </style>