Hi guys

On this page I have 4 different radio inputs

I need a pop up box everytime one of them isnt filled in

How can I do this?

PHP Code:
<script Language="JavaScript">

<!--

function board_checker()

{



    var radios = document.getElementById('radio_form').getElementsByTagName('INPUT');

    for(var i = 0; i < radios.length; i++) {

        if(radios[i].type == 'radio') {

            if(radios[i].checked)

                return true;

        }

    }



    alert("Please select a script.")

    



    return false;





}

-->

</script>

   <font size="4">

<B>Options</b></font>

<br>

<br>

<font size="3" face="century gothic">

  Products  <b>Options  </b> Personal Details  Processor  Payment<br></font>

<font size="3">Step 2 of 5</font><br><bR></font>

  <table width="100%"><tr><td width="60%">





<form  method="get" action="details.php" name="radio_form" onsubmit="return board_checker()">



 <input type="hidden" name="board" value="<? echo"$board"?>">



<table>

<tr>

<td><font size="3" face="century gothic">

 <input type="radio" name="design" value="yes">yes

</td>

<td><font size="3" face="century gothic">

 <input type="radio" name="design" value="no">no

</td>



<td>

<font size="3" face="century gothic">

<b>Custom site design</b>

<Br>

Our team of designers can design your Job Script to your exact specification. We will also implemtent the design into the software. Designs normally 



take 5 - 7 days.

<Br>

</td>

<td width="200">

<center><font size="3" face="century gothic"><b>750</b></center>

</td>

</tr>





<tr>

<td><font size="3" face="century gothic">

 <input type="radio" name="install" value="yes">yes

</td><td><font size="3" face="century gothic">

 <input type="radio" name="install" value="no">no

</td>

<td><font size="3" face="century gothic">

<b>Instalation</b>

<br>

Our team of programmers can take the hassle of installing your script by installing the software. All Installations are complete within 24 hours of 



recieving server details.

</td>

<td width="200">

<center><font size="3" face="century gothic"><b>50</b></center>

</td>

</tr>





<tr>

<td><font size="3" face="century gothic">

 <input type="radio" name="hosting" value="yes">yes

</td><td><font size="3" face="century gothic">

 <input type="radio" name="hosting" value="no">no

</td>

<td><font size="3" face="century gothic">

<B>Hosting</b>

<br>

We provide hosting for all of our software. Your hosting account will be live instantly after checkout.

</td>

<td width="200"><center>

<font size="3" face="century gothic"><B>19.99 / Month</b> </center>

</td>

</tr>









<tr>

<td><font size="3" face="century gothic">

 <input type="radio" name="mod" value="yes">yes

</td><td><font size="3" face="century gothic">

 <input type="radio" name="mod" value="no">no

</td>

<td><font size="3" face="century gothic">

<B>Modifications</b>

<br>

Our programmers can add modifications to the software if needed. We will contact you via yuor preffered method to discuss what modifications you 



want.

</td>

<td>

<center>

<font size="3" face="century gothic"><B>Quote</b> </center>

</td>

</tr>

</table>

<Br>

<input type="submit" value="Continue">

</form>