<!DOCTYPE html>
<html>
<head>
<style type="text/css">
#box {
display: none;
}
</style>
<script type="text/javascript">
function test(self, On) {
document.getElementsByName(On ? 'anonim_da' : 'anonim_net')[0].checked = false;
document.getElementById('box').style.display=(self.checked && On)? 'block': 'none';
};
</script>
</head>
<body>
<input type="checkbox" name="anonim_da" onclick="test(this)" checked />
<br />
<input type="checkbox" name="anonim_net" onclick="test(this, true)" />
<div id="box">
<p>Text</p>
</div>
</body>
</html>