allow for form validation without leaving page

form validation onsubmit

     <script language="JavaScript" type="text/javascript">
<!--
     function CheckForm() {
  	 	 if (!(document.contactForm.name.value.length > 0))
            {
            alert("You must enter your Name");
			contactForm.name.focus();
            return false;
            }


		 	if (!(document.contactForm.email.value.length > 0))
            {
            alert("You must enter your Email Address");
			contactForm.email.focus();
            return false;
            }
			if (!(document.contactForm.phone.value.length > 0))
            {
            alert("You must enter your Phone Number");
			contactForm.phone.focus();
            return false;
            }
	    		if (document.contactForm.security.value != 'white')
            {
            alert("Your Security code is incorrect");
			contactForm.security.focus();
            return false;
            }

        return true;
    }
//-->

</script>

 <form action="/contact.htm" method="post" enctype="multipart/form-data" name="contactForm" id="contactForm" onSubmit="return CheckForm();">