Check Box Validation JavaScript

<script type="text/javascript" language="JAVASCRIPT">
function checkCheckBoxes() {
if (document.forms[0].chk_terms.checked == false){
alert ("You didn\'t choose terms and conditions.");
return false;
}
}
</script>


<input type="checkbox" name="chk_terms" value="terms"> I agree;

<input type="submit" name="btn_submit" value="Save" onclick="return checkCheckBoxes();" class="button"/>