function postit() { // check postcode format is valid
	test = document.form_registration.post_code.value;
	size = test.length
	test = test.toUpperCase(); // Change to uppercase
	while (test.slice(0, 1) == " ") // Strip leading spaces
	{
		test = test.substr(1, size - 1);
		size = test.length
	}
	while (test.slice(size - 1, size) == " ") // Strip trailing spaces
	{
		test = test.substr(0, size - 1);
		size = test.length
	}
	document.form_registration.post_code.value = test; // write back to form field
	if (size < 6 || size > 8) { // Code length rule
		alert(test + " IS NOT A VALID POSTCODE - WRONG LENGTH");
		document.form_registration.post_code.focus();
		return false;
	}
	if (!(isNaN(test.charAt(0)))) { // leftmost character must be alpha
									// character rule
		alert(test + " IS NOT A VALID POSTCODE - CANNOT START WITH A NUMBER");
		document.form_registration.post_code.focus();
		return false;
	}
	if (isNaN(test.charAt(size - 3))) { // first character of inward code must
										// be numeric rule
		alert(test
				+ " IS NOT A VALID POSTCODE - ALPHA CHARACTER IN WRONG POSITION");
		document.form_registration.post_code.focus();
		return false;
	}
	if (!(isNaN(test.charAt(size - 2)))) { // second character of inward code
											// must be alpha rule
		alert(test + " IS NOT A VALID POSTCODE - NUMBER IN WRONG POSITION");
		document.form_registration.post_code.focus();
		return false;
	}
	if (!(isNaN(test.charAt(size - 1)))) { // third character of inward code
											// must be alpha rule
		alert(test + " IS NOT A VALID POSTCODE - NUMBER IN WRONG POSITION");
		document.form_registration.post_code.focus();
		return false;
	}
	if (!(test.charAt(size - 4) == " ")) {// space in position length-3 rule
		alert(test
				+ " IS NOT A VALID POSTCODE - NO SPACE OR SPACE IN WRONG POSITION");
		document.form_registration.post_code.focus();
		return false;
	}
	count1 = test.indexOf(" ");
	count2 = test.lastIndexOf(" ");
	if (count1 != count2) {// only one space rule
		alert(test + " IS NOT A VALID POSTCODE - ONLY ONE SPACE ALLOWED");
		document.form_registration.post_code.focus();
		return false;
	}
	//alert("Postcode Format OK");
	return true;
}