@keyframes fadein {
from { opacity: 0.3; }
to { opacity: 1; } /* Padrão */
}
@-moz-keyframes fadein {
from { opacity: 0.3; }
to { opacity: 1; } /* Firefox */
}
@-webkit-keyframes fadein {
from { opacity: 0.3; }
to { opacity: 1; } /* Webkit */
}
@-ms-keyframes fadein {
from { opacity: 0.3; }
to { opacity: 1; } /* IE */
}​

@keyframes fadeout {
from { opacity: 1; }
to { opacity: 0.3; } /* Padrão */
}
@-moz-keyframes fadeout {
from { opacity: 1; }
to { opacity: 0.3; } /* Firefox */
}
@-webkit-keyframes fadeout {
from { opacity: 1; }
to { opacity: 0.3; } /* Webkit */
}
@-ms-keyframes fadeout {
from { opacity: 1; }
to { opacity: 0.3; } /* IE */
}​