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<div>Hello World</div>

div { 
    animation: pulse 2s infinite; /* CSS3 */
    -moz-animation: pulse 2s infinite; /* Firefox */
    -webkit-animation: pulse 2s infinite; /* Webkit */ 
    font-size: 4em; 
    text-align: center;
}

@keyframes pulse { /* CSS3 */
    0%, 100% {color: white;}
    50% {color: black;}
} 

@-moz-keyframes pulse { /* Firefox */
    0%, 100% {color: white;}
    50% {color: black;}
} 

@-webkit-keyframes pulse { /* Webkit */
    0%, 100% {color: white;}
    50% {color: black;}
}