Radion Buttons Error

The error here that if i gave each radio button different name the function will work but if i gave all the radio button the same name but different values the function stop working ......

<script type="text/JavaScript">
<!--
function OU()
{
day = new Date();
id = day.getTime();
x=document.form1
fn = x.a.value
alert (fn)
ln = x.k.value
 
submitOK="True"
var url="vote.php"
url=url+"?qid="+fn
url=url+"&R1="+ln
alert (url)
eval("page" + id + " = window.open(url, '" + id + "', 'toolbar=0,scrollbars=0,location=1,statusbar=0,menubar=0,resizable=0,width=750,height=200,left = 301,top = 332');");
}
//-->
</script>

HTML4Strict Code:
<form method="POST" name="form1" action="" onsubmit="OU()">
    <p dir="rtl" align="left">a<input type="radio" value="a" name="k"><br>
    b<input type="radio" value="b" name="k"><br>
    c<input type="radio" value="c" name="k"><br>
    d<input type="radio" value="d" name="k"><br>
    &nbsp;</p>
    <p align="left"><input type="submit" value="Submit" name="B1"><input type="reset" value="Reset" name="B2"></p>
</form>