Infinity178,
<!DOCTYPE HTML>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<style type="text/css">
[value="1"] ~ .wp{
display: none;
}
[value="1"]:checked ~ .wp{
display: block;
}
</style>
</head>
<body>
<div class="main">
<input type="radio" name="radio[val][]" id="val-1" value="1" />
<input type="radio" name="radio[val][]" id="val-0" value="0" />
<div class="wp">
<div id="block">txt</div>
</div>
</div>
</body>
</html>