Validation Script?

[Antec]

Ok, i know nothing about javascripting lol but i need someone's help in creating a validation script for a form i have...the script would need to validate a text field, email field and require the checkbox be checked off in order to submit the form, and if there is any errors i would like it to pop-up a little window with the error message...here is the coding it needs to go into...i thank anyone in advanced that can help me.

 

/*
BEGINS for JoinUS
*/
if($_GET['view'] == "JoinUs") {
require("functions.php");				
$query = @mysql_query("SELECT recruiting, security_status, total FROM status");
$row_status = mysql_fetch_array($query);

if($row_status['total'] >= 350 || $row_status['recruiting'] == 1) {
                    echo' <font color="#76A5D5" size="4" face="verdana"><b>Recruiting Is Closed!</b></font>';
				} else {


echo '
<form method="post" name="JoinRequest" action="sendit.php">';


$ipi = getenv("REMOTE_ADDR");
$httprefi = getenv ("HTTP_REFERER");
$httpagenti = getenv ("HTTP_USER_AGENT");
?>

<input type="hidden" name="ip" value="<?php echo $ipi ?>"/>
<input type="hidden" name="httpref" value="<?php echo $httprefi ?>"/>
<input type="hidden" name="httpagent" value="<?php echo $httpagenti ?>"/>
<br />
<b><font color="#76A5D5" size="2" face="verdana">Socom Name:  </font></b>
<input name="visitor" type="text" id="visitor" size="35"/>
<br />
<br />
<b><font color="#76A5D5" size="2" face="verdana">Email Address:</font></b> 
<input type="text" name="visitormail" size="35"/>
<br />
<br />
<b><font color="#76A5D5" size="2" face="verdana">Version Trying For:</font></b> 
<select name="attn" size="1">
<option value=" Socom1 ">Socom </option>
<option value=" Socom2 ">Socom 2 </option>
<option value=" Socom3 ">Socom 3 </option>
<option value=" Socom4 ">Combined Assult </option>
</select>
<br /><br />
<input type="checkbox" name="notes" value="checkbox"/>
<font color="#76A5D5" size="1" face="verdana">I Have Read And Agree To Follow The <strong><a href="index.php?view=Rules">Clan Rules</font></a></strong><br />
<br />
<input type="submit" value="Submit" name="submit_button">
</form>
<font color="#FF0000">**</font><font color="#76A5D5" size="1" face="verdana">All  Applications will be reviewed in a timely manner. Any questions or concerns belong on our <b><a href="forum/index.php">Forum</a></b></font><br />
<br />
<?php
}
include('footer.php');
}
/*
ENDS for HowTojoin
*/