IF RADIO1=CHECKED   THEN DO THIS      

ELSE
IF RADIO2=CHECKED THEN DO THAT

if (document.form1.radio[0].checked){
DO THIS
} else if (document.form1.radio[1].checked){
DO THIS
}

<form method="post" name="form1">
<input type="radio" name="radio[0]" value="radio[0]"> Select this to upload picture to the server: <br>
<input type="radio" name="radio[0]" value="radio[0]"> select this insert a PictureURL:<br>
</form>


<script language="JavaScript">
if (document.form1.radio[0].checked){
</script>


<?php echo "upload"; ?>

<script language="JavaScript">
} else if (document.form1.radio[1].checked){
</script>

<?php
echo 'type in a picture URL:<br><input type="text" name="pictureURL" size="30" value="http://"><br>'; 
?>
<script language="JavaScript">
}
</script>

<form method="POST" action="--WEBBOT-SELF--" name="post">
  <p>
  هل تحب البطيخ</p>
  <p>&nbsp;نعم<input type="radio" value="V1" name="R1"></p>
  <p>&nbsp;لا <input type="radio" value="V2" checked name="R1"></p>
  <p><input type="button" value="انقر" name="B1" onclick="s()"></p>
</form>
<script>
function s()
{
if(post.R1[0].checked)
{
alert("انت اخترت نعم");
}else if(post.R1[1].checked){
alert("انت اخترت لاالالالالا");
}
}
</script>