<script type="text/javascript">

	function sec(deger){
		if(deger == 1){
			document.getElementById("yazdir").innerHTML = "Alan 1 secilince yazilacak";
		}
		else if(deger == 2){
			document.getElementById("yazdir").innerHTML = "Alan 2 secilince yazilacak";
		}
		else {
			document.getElementById("yazdir").innerHTML= "Alan 3 secilince yazilacak";
		}
	}

</script>

<input type="radio" name="radioname" value="1" onclick="sec(1)"> Alan 1 <br>
<input type="radio" name="radioname" value="2" onclick="sec(2)"> Alan 2 <br>
<input type="radio" name="radioname" value="3" onclick="sec(3)"> Alan 3 <br>
<div id="yazdir"></div>