// JavaScript Document
function CheckForm()
{
	if (document.reg.email.value == "")
	{
		alert("Please enter your email.");
		document.reg.email.focus();
		return false;
	}

	if (document.reg.first.value == "")
	{
		alert("Please enter your first name.");
		document.reg.first.focus();
		return false;
	}
	if (document.reg.last.value == "")
	{
		alert("Please enter your last name.");
		document.reg.last.focus();
		return false;
	}
	return emailCheck(document.reg.email.value);
}

		function emailCheck(emailStr)
		{
			/* The following variable tells the rest of the function whether or not
			to verify that the address ends in a two-letter country or well-known
			TLD.  1 means check it, 0 means don't. */

			var checkTLD=1;

			/* The following is the list of known TLDs that an e-mail address must end with. */

			var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;

			/* The following pattern is used to check if the entered e-mail address
			fits the user@domain format.  It also is used to separate the username
			from the domain. */

			var emailPat=/^(.+)@(.+)$/;

			/* The following string represents the pattern for matching all special
			characters.  We don't want to allow special characters in the address.
			These characters include ( ) < > @ , ; : \ " . [ ] */

			var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";

			/* The following string represents the range of characters allowed in a
			username or domainname.  It really states which chars aren't allowed.*/

			var validChars="\[^\\s" + specialChars + "\]";

			/* The following pattern applies if the "user" is a quoted string (in
			which case, there are no rules about which characters are allowed
			and which aren't; anything goes).  E.g. "jiminy cricket"@disney.com
			is a legal e-mail address. */

			var quotedUser="(\"[^\"]*\")";

			/* The following pattern applies for domains that are IP addresses,
			rather than symbolic names.  E.g. joe@[123.124.233.4] is a legal
			e-mail address. NOTE: The square brackets are required. */

			var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;

			/* The following string represents an atom (basically a series of non-special characters.) */

			var atom=validChars + '+';

			/* The following string represents one word in the typical username.
			For example, in john.doe@somewhere.com, john and doe are words.
			Basically, a word is either an atom or quoted string. */

			var word="(" + atom + "|" + quotedUser + ")";

			// The following pattern describes the structure of the user

			var userPat=new RegExp("^" + word + "(\\." + word + ")*$");

			/* The following pattern describes the structure of a normal symbolic
			domain, as opposed to ipDomainPat, shown above. */

			var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");

			/* Finally, let's start trying to figure out if the supplied address is valid. */

			/* Begin with the coarse pattern to simply break up user@domain into
			different pieces that are easy to analyze. */

			var matchArray=emailStr.match(emailPat);

			if (matchArray==null) {
			  /* Too many/few @'s or something; basically, this address doesn't
			  even fit the general mould of a valid e-mail address. */

			  alert("Email address seems incorrect (check @ and .'s)");
			  return false;
			}

			var user=matchArray[1];
			var domain=matchArray[2];

			// Start by checking that only basic ASCII characters are in the strings (0-127).

			for (i=0; i<user.length; i++) {
			  if (user.charCodeAt(i)>127) {
				alert("Ths username contains invalid characters.");
				return false;
			  }
			}

			for (i=0; i<domain.length; i++) {
			  if (domain.charCodeAt(i)>127) {
				alert("Ths domain name contains invalid characters.");
				return false;
			  }
			}

			// See if "user" is valid
			if (user.match(userPat)==null) {
			  // user is not valid
			  alert("The username doesn't seem to be valid.");
			  return false;
			}

			/* if the e-mail address is at an IP address (as opposed to a symbolic
			host name) make sure the IP address is valid. */

			var IPArray=domain.match(ipDomainPat);

			if (IPArray!=null) {
			  // this is an IP address
			  for (var i=1;i<=4;i++) {
				if (IPArray[i]>255) {
				  alert("Destination IP address is invalid!");
				  return false;
				}
			  }
			  return true;
			}

			// Domain is symbolic name.  Check if it's valid.
			var atomPat=new RegExp("^" + atom + "$");
			var domArr=domain.split(".");
			var len=domArr.length;

			for (i=0;i<len;i++) {
			  if (domArr[i].search(atomPat)==-1) {
				alert("The domain name does not seem to be valid.");
				return false;
			  }
			}

			/* domain name seems valid, but now make sure that it ends in a
			known top-level domain (like com, edu, gov) or a two-letter word,
			representing country (uk, nl), and that there's a hostname preceding
			the domain or country. */

			if (checkTLD && domArr[domArr.length-1].length!=2 && domArr[domArr.length-1].search(knownDomsPat)==-1) {
			  alert("The address must end in a well-known domain or two letter " + "country.");
			  return false;
			}

			// Make sure there's a host name preceding the domain.
			if (len<2) {
			  alert("This address is missing a hostname!");
			  return false;
			}

			// If we've gotten this far, everything's valid!
			return true;
			}