function emailCheck (emailStr) {
	var checkTLD=1;
	var knownDomsPat=/^(com|net|org|edu|int|mil|gov|arpa|biz|aero|name|coop|info|pro|museum)$/;
	var emailPat=/^(.+)@(.+)$/;
	var specialChars="\\(\\)><@,;:\\\\\\\"\\.\\[\\]";
	var validChars="\[^\\s" + specialChars + "\]";
	var quotedUser="(\"[^\"]*\")";
	var ipDomainPat=/^\[(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})\]$/;
	var atom=validChars + '+';
	var word="(" + atom + "|" + quotedUser + ")";
	var userPat=new RegExp("^" + word + "(\\." + word + ")*$");
	var domainPat=new RegExp("^" + atom + "(\\." + atom +")*$");
	var matchArray=emailStr.match(emailPat);

	if (matchArray==null) {
	  alert("Email address seems incorrect (check @ and .'s)");
	  return false;
	}
	var user=matchArray[1];
	var domain=matchArray[2];
	for (i=0; i<user.length; i++) {
	  if (user.charCodeAt(i)>127) {
	    alert("The email field contains invalid characters.");
	    return false;
	  }
	}
	for (i=0; i<domain.length; i++) {
	  if (domain.charCodeAt(i)>127) {
	    alert("The email domain name contains invalid characters.");
	    return false;
	  }
	}

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

	var IPArray=domain.match(ipDomainPat);
	if (IPArray!=null) {
	  for (var i=1;i<=4;i++) {
	    if (IPArray[i]>255) {
	      alert("The email Destination IP address is invalid!");
	      return false;
	    }
	  }
	  return true;
	}

	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 email domain name does not seem to be valid.");
	    return false;
	  }
	}

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

	if (len<2) {
	  alert("This email address is missing a hostname!");
	  return false;
	}
return true;
}

function joinup_Validator(theForm)
{
  if (theForm.first_name.value == "")
  {
    alert("Please enter your \"First Name\".");
    theForm.first_name.focus();
    return (false);
  }
  if (theForm.surname.value == "")
  {
    alert("Please enter your \"Surname\".");
    theForm.surname.focus();
    return (false);
  }
// If all phone fields empty, then force entry of one
  if ((theForm.phone_area_code.value == "") && (theForm.day_phone.value == "") && (theForm.mobile_prefix.value == "") && (theForm.mobile_ext.value == ""))
  {
    alert("You must supply at least one phone number contact.");
    theForm.phone_area_code.focus();
    return (false);
  }
// Now one field is used so check it's partner field
  if (((theForm.phone_area_code.value != "") && (theForm.day_phone.value == "")) ||((theForm.phone_area_code.value == "") && (theForm.day_phone.value != "")) )
  {
    alert("Please complete your phone number contact.");
    if (theForm.phone_area_code.value == "") {
      theForm.phone_area_code.focus();
    }
    if (theForm.day_phone.value == "") {
      theForm.day_phone.focus();
    }
    return (false);
  }
  
  if (((theForm.mobile_prefix.value != "") && (theForm.mobile_ext.value == "")) ||((theForm.mobile_prefix.value == "") && (theForm.mobile_ext.value != "")) )
  {
    alert("Please complete your mobile number contact.");
    if (theForm.mobile_prefix.value == "") {
      theForm.mobile_prefix.focus();
    }
    if (theForm.mobile_ext.value == "") {
      theForm.mobile_ext.focus();
    }
    return (false);
  }
<!---- Day Phone ---------->
  if ((theForm.phone_area_code.value != "") && (theForm.phone_area_code.value.length < 2))
  {
    alert("Please enter your full 2 digit area code.");
    theForm.phone_area_code.focus();
    return (false);
  }  
// Now check for numeric entry only in any non-empty phone field
  var checkOK = "0123456789";
  var checkStr = theForm.phone_area_code.value;
  var allValid = true;
  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only digits in the \"area code\" field.");
    theForm.phone_area_code.focus();
    return (false);
  }
  if ((theForm.day_phone.value != "") && (theForm.day_phone.value.length < 8))
  {
    alert("Please enter your full 8 digit mobile number.");
    theForm.day_phone.focus();
    return (false);
  }  
// Now check for numeric entry only in any non-empty phone field
  var checkOK = "0123456789 -";
  var checkStr = theForm.mobile_ext.value;
  var allValid = true;
  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only digits and a space character in the \"day phone\" field.");
    theForm.day_phone.focus();
    return (false);
  }
  if ((checkStr.indexOf(" "))!=(checkStr.lastIndexOf(" "))) {
    alert("Too many space characters in the \"day phone\" field.");
    theForm.day_phone.focus();
    return (false);
  }

<!---- Mobile Number ------>
  if ((theForm.mobile_prefix.value != "") && (theForm.mobile_prefix.value.length < 4))
  {
    alert("Please enter your full 4 digit mobile prefix.");
    theForm.mobile_prefix.focus();
    return (false);
  }  
// Now check for numeric entry only in any non-empty phone field
  var checkOK = "0123456789";
  var checkStr = theForm.mobile_prefix.value;
  var allValid = true;
  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only digits in the \"mobile prefix\" field.");
    theForm.mobile_prefix.focus();
    return (false);
  }
  if ((theForm.mobile_ext.value != "") && (theForm.mobile_ext.value.length < 6))
  {
    alert("Please enter your full 6 digit mobile number.");
    theForm.mobile_ext.focus();
    return (false);
  }  
// Now check for numeric entry only in any non-empty phone field
  var checkOK = "0123456789 -";
  var checkStr = theForm.mobile_ext.value;
  var allValid = true;
  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only digits and a space character in the \"mobile number\" field.");
    theForm.mobile_ext.focus();
    return (false);
  }
  if ((checkStr.indexOf(" "))!=(checkStr.lastIndexOf(" "))) {
    alert("Too many space characters in the \"mobile number\" field.");
    theForm.mobile_ext.focus();
    return (false);
  }
  
<!---- Email field ------>
  if (theForm.email.value == "")
  {
    alert("Please enter your \"Email Address\".");
    theForm.email.focus();
    return (false);
  }
  var checkOK = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-@-_.";
  var checkStr = theForm.email.value;
  var allValid = true;
  for (i = 0;  i < checkStr.length;  i++)
  {
    ch = checkStr.charAt(i);
    for (j = 0;  j < checkOK.length;  j++)
      if (ch == checkOK.charAt(j))
        break;
    if (j == checkOK.length)
    {
      allValid = false;
      break;
    }
  }
  if (!allValid)
  {
    alert("Please enter only letter, digit and \"@-_.\" characters in the \"Email Address\" field.");
    theForm.email.focus();
    return (false);
  }
  if (emailCheck(theForm.email.value)) {
  } else {
      theForm.email.focus();
      return (false);  
  }
  return (true);
}

function submit_button_onclick() {
  if (joinup_Validator(document.forms[0])) {
    document.forms[0].submit();
    return true;
  }
}