function submitform()
{
  var errorMsg = "Unable to send your feedback because :\n";  // default error message
  var errorReason = "";  // to hold actual error reasons
	var focusItem = "";   // to hold name of input to focus on
  
  // check user has entered a name
  if ( document.forms[0].txtName.value=="" )
  {
    errorReason += "  * You have not entered a name\n";
		focusItem = "txtName";
  } else if (InvalidName(document.forms[0].txtName.value)) {
    errorReason += "  * Your name may only contain letters and spaces.\n";
		focusItem = "txtName";
  }
  
  // check that the email is valid
  if (document.forms[0].txtEmail.value=="" || InvalidEmail(document.forms[0].txtEmail.value))
  {
    errorReason += "  * Your Email address is not valid\n";
		if ( focusItem == "" ) focusItem = "txtEmail";
  }

  if (document.forms[0].txtComment.value=="")
  {
    errorReason += "  * You have not entered any feedback!\n";
		if ( focusItem == "" ) focusItem = "txtComment";
  }
  
  // if there are any errors display them, otherwise submit the form
  if (!(errorReason=="" ))
  {
    alert(errorMsg + errorReason);
		eval("document.forms[0]." + focusItem + ".focus()");
    return false;
  } else {
    return true;
  }
}

// checks for a valid email address using regular expressions
function InvalidEmail(email)
{
  var filter = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9])+$/;
  return !(filter.test(email));
}

// checks for a valid name using regular expressions
function InvalidName (name)
{
  var filter = /^([a-zA-Z\s])+$/;
  return !(filter.test(name));
}