Check box validation

[niths]

hi all,
i am having a page where there are some checkboxes in it. i cant give exact number because i am getting that from database. so now if the user didnt check atleast one check box i need to get a popup. so can any one help me please..its urgent..
Thank u..

<table border="1" cellspacing="0" cellpadding="0" align="center" style="width: 500px" bordercolor="red">
    <tr>
        <th></th>
        <th style="color: navy;">Userid</th>
        <th style="color: navy;">Username</th>
 
    </tr>
    <?php
    $sno=1;
    while($row=mysql_fetch_array($result2, MYSQL_ASSOC)){
    ?>
     <tr>
<td><input name="checkbox[]" type="checkbox" id="checkbox[]" value="<? echo $row['userid']; ?>"></td>
<td><? echo $row['userid']; ?></td>
<td><? echo $row['username'];?></td>
</tr>
<?php
    $sno=$sno+1;
}
?>
    </table>

[Dormilich]

a popup is a client-side action, thus PHP can’t be (directly) involved.

to check whether no checkbox was selected, loop over all checkboxes and test for the .checked property.

// returns true if at least one box is checked, otherwise false
function checkBox()
{
    var i, list = document.forms[0]["checkbox[]"];
    for (i = list.length; i--;) {
        if (list[i].checked) {
            return true;
        }
    }
    return false;
}