Animaciones básicas con CSS transition

<!doctype html>
<html lang="es">
<head>
<meta charset="utf-8">
<title>Animaciones básicas con CSS transition</title>
</head>
<body>

#div1 {
    -webkit-transition-timing-function: linear;
    -moz-transition-timing-function: linear;
    -o-transition-timing-function: linear;
    transition-timing-function: linear;
}
#div2 {
    -webkit-transition-timing-function: ease;
    -moz-transition-timing-function: ease;
    -o-transition-timing-function: ease;
    transition-timing-function: ease;
}
#div3 {
    -webkit-transition-timing-function: ease-in;
    -moz-transition-timing-function: ease-in;
    -o-transition-timing-function: ease-in;
    transition-timing-function: ease-in;
}
#div4 {
    -webkit-transition-timing-function: ease-out;
    -moz-transition-timing-function: ease-out;
    -o-transition-timing-function: ease-out;
    transition-timing-function: ease-out;
}
#div5 {
    -webkit-transition-timing-function: ease-in-out;
    -moz-transition-timing-function: ease-in-out;
    -o-transition-timing-function: ease-in-out;
    transition-timing-function: ease-in-out;
}

div:hover {
    width: 300px;
    background: #428bca;
}
</style>

<div id="div1">linear</div>
<div id="div2">ease</div>
<div id="div3">ease-in</div>
<div id="div4">ease-out</div>
<div id="div5">ease-in-out</div>

</body>
</html>