Grazie molto gentile… se posso approfittare perchè con questo codice non funziona?

@-webkit-keyframes fadeInLeft {
0% {
opacity: 0;
-webkit-transform: translateX(-20px);
}

100% {
opacity: 1;
-webkit-transform: translateX(0);
}
}

@-moz-keyframes fadeInLeft {
0% {
opacity: 0;
-moz-transform: translateX(-20px);
}

100% {
opacity: 1;
-moz-transform: translateX(0);
}
}

@-ms-keyframes fadeInLeft {
0% {
opacity: 0;
-ms-transform: translateX(-20px);
}

100% {
opacity: 1;
-ms-transform: translateX(0);
}
}

@-o-keyframes fadeInLeft {
0% {
opacity: 0;
-o-transform: translateX(-20px);
}

100% {
opacity: 1;
-o-transform: translateX(0);
}
}

@keyframes fadeInLeft {
0% {
opacity: 0;
transform: translateX(-20px);
}

100% {
opacity: 1;
transform: translateX(0);
}
}

.fadeInLeft {
background-color: #CC99FF; width:400px; height:300px;/* puramente indicativi */

-webkit-animation-name: fadeInLeft;
-moz-animation-name: fadeInLeft;
-ms-animation-name: fadeInLeft;
-o-animation-name: fadeInLeft;
animation-name: fadeInLeft;
}

<body>

<div class="fadeInLeft">Ciao</div>

</body>