<html>
<head>

<script type="text/javascript" language="JavaScript">
function checkscript() {

var boxesTicked = ""

for (i = document.getElementsByName('chkboxes').length - 1; i >= 0; i--) {

if (document.getElementsByName('chkboxes')[i].checked) {

boxesTicked = boxesTicked + document.getElementsByName('chkboxes')[i].value + "\n"

}

}

if (boxesTicked == "") {
alert ("You must select a box to continue.")
return false
}
else {
alert (boxesTicked)
return true;
}

}

</script>

<title>Javascript that validates checkboxes</title>
</head>

<body>

<form name="f1" method="POST" action= "step2.php" onsubmit="return checkscript()">
<input type='checkbox' name='chkboxes' value='1'> 1<br>
<input type='checkbox' name='chkboxes' value='2'> 2<br>
<input type='checkbox' name='chkboxes' value='3'> 3<br>
<br>
<input type="submit" value="Continue to Step 2..." name="s2"></p>
</form>

</body>
</html>