function validate_email ( value )
{
apos=value.indexOf("@");
dotpos=value.lastIndexOf(".");
if (apos<1||dotpos-apos<2)
{
return false;
}
else
{
return true;
}
}


/*
 phone number validation script.)
 */

// Declaring required variables
var digits = "0123456789";
// non-digit characters which are allowed in phone numbers
var phoneNumberDelimiters = "()- ";
// characters which are allowed in international phone numbers
// (a leading + is OK)
var validWorldPhoneChars = phoneNumberDelimiters + "+";
// Minimum no of digits in an international phone no.
var minDigitsInIPhoneNumber = 10;

function isInteger(s)
{   var i;
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character is number.
        var c = s.charAt(i);
        if (((c < "0") || (c > "9"))) return false;
    }
    // All characters are numbers.
    return true;
}

function stripCharsInBag(s, bag)
{   var i;
    var returnString = "";
    // Search through string's characters one by one.
    // If character is not in bag, append to returnString.
    for (i = 0; i < s.length; i++)
    {   
        // Check that current character isn't whitespace.
        var c = s.charAt(i);
        if (bag.indexOf(c) == -1) returnString += c;
    }
    return returnString;
}

function checkInternationalPhone(strPhone){
s=stripCharsInBag(strPhone,validWorldPhoneChars);
return (isInteger(s) && s.length >= minDigitsInIPhoneNumber);
}

function checkform ( form )
{

  // ** START **
  if (form.email.value == "" || !validate_email ( form.email.value ) ) {
    alert( "Please enter a valid email address.");
    form.email.focus();
    return false ;
  }
  // ** END **
  
    // ** START **
  if (form.forename.value == "") {
    alert( "Please enter your forename." );
    form.forename.focus();
    return false ;
  }
  // ** END **
  
    // ** START **
  if (form.surname.value == "") {
    alert( "Please enter your surname." );
    form.surname.focus();
    return false ;
  }
  // ** END **
  
    // ** START **
  if (form.telephone.value == "" || !checkInternationalPhone ( form.telephone.value )) {
    alert( "Please enter a valid contact number." );
    form.telephone.focus();
    return false ;
  }
  // ** END **
  
    // ** START **
  if (form.message.value == "") {
    alert( "Please enter your comment/query." );
    form.message.focus();
    return false ;
  }
  // ** END **
  return true ;
}