<input type="radio" name="test" value="v1" checked><input type="radio" name="test" value="v1" checked><input type="radio" name="test" value="v1" checked>
<input type=button onclick="far()" value="go">
<script>
function far()
{
var chk=false;
var a=document.getelementsbyname('test');
for(i=0;i<a.length;i++)
{
if(a.checked){
chk=true;
break;
}
}
if(!chk)
{
alert("please select one of the radios!!!");
}
}
</script>