function verifyRequired(f)
	{
	var msg = "";
	var empty_fields = "";
	var email_errors = "";
	
	for (var i = 0; i < f.length; i++)
		{
		var e = f.elements[i];
		// checks if empty
		if (e.required==true)  // calls isblank function, below
			{
			if (e.value==null || e.value=="" || isblank(e.value))
				{
				if (e.title)
					{
					empty_fields += "\n  - " + e.title;
					}
				else
					{
					empty_fields += "\n  - " + e.name;
					}
				}
			else if (e.name=="email")
				{
				email_errors = emailErrorCheck(e.value);
				}
			}
		}

	// if errors, display messages and return false to prevent form submission
	// otherwise return true
	
	if (empty_fields)
		{
		msg += "________________________________________\n\n"	
		msg += "All required fields must be completed.\n"
		msg += "Please complete the following fields and re-submit:\n"
		msg += "________________________________________\n"
		msg += empty_fields
		msg += "\n"
		alert(msg);
		return false;
		}
	else if (email_errors)
		{
		msg += "Please correct the email address.\n"
		msg += "(" + email_errors + ")"
		msg += "\n"
		alert(msg);
		return false;
		}

	else return true;
	}

// isblank: utility function that returns true if
// a string contains only whitespace characters (used in verifyRequired)
function isblank(s)
	{
	for (var i = 0; i<s.length; i++)
		{
		var  c = s.charAt(i);
		if ((c != ' ') && (c != '|n') && (c != '\t')) return false;
		}
	}


function emailErrorCheck(emailStr)
	{
	/* 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 +")*$")
	var email_errors = "";
	
	/* 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. */
		email_errors += "It seems incorrectly formatted -- check @ and .'s."
		return email_errors
	}
	var user=matchArray[1]
	var domain=matchArray[2]
	
	// See if "user" is valid 
	if (user.match(userPat)==null) {
	    // user is not valid
	    email_errors += "The username doesn't seem to be valid."
	    return email_errors
	}
	
	/* 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) {
		        email_errors += "The destination IP address is invalid."
			return email_errors
		    }
	    }
	    return false
	}
	
	// Domain is symbolic name
	var domainArray=domain.match(domainPat)
	if (domainArray==null) {
		email_errors += "The domain name doesn't seem to be valid."
	    return email_errors
	}
	
	/* domain name seems valid, but now make sure that it ends in a
	   three-letter word (like com, edu, gov) or a two-letter word,
	   representing country (uk, nl), and that there's a hostname preceding 
	   the domain or country. */
	
	/* Now we need to break up the domain to get a count of how many atoms
	   it consists of. */
	var atomPat=new RegExp(atom,"g")
	var domArr=domain.match(atomPat)
	var len=domArr.length
	if (domArr[domArr.length-1].length<2 || 
	    domArr[domArr.length-1].length>3) {
	   // the address must end in a two letter or three letter word.
	   email_errors += "It must end in a three-letter domain or a two-letter country code."
	   return email_errors
	}
	
	// Make sure there's a host name preceding the domain.
	if (len<2) {
	   email_errors += "It is missing a hostname or domain name."
	   return email_errors
	}
	
	// If we've gotten this far, there are no known errors.
	return false;
	}