자연스럽게 사라지는 CSS

<style>

input[type=checkbox]:checked + div {

height:0;

}

div {

border : 1px;

background-color:gray;

opacity:0.8;

overflow : hidden;

width:650px; height:400px;

-ms-transition-duration:0.5s;

-webkit-transition-duration:0.5s;

-moz-transition-duration:0.5s;

-o-transition-duration:0.5s;

transition-duration:0.5s;

}

</style>