[Aetae]

css3

<style>
input[type="checkbox"] ~ div#d1,
input[type="checkbox"]:checked ~ div#d2{
    display:none;
}
input[type="checkbox"]:checked ~ div#d1{
    display:block;
}
</style>
<input type="checkbox">
<div id="d1">1</div>
<div id="d2">2</div>