var req;

function getXmlHttpRequestObject()
{
	if(window.XMLHttpRequest)
	{
		return new XMLHttpRequest(); //Not IE
	}
	else if(window.ActiveXObject)
	{
		return new ActiveXObject("Microsoft.XMLHTTP"); //IE
	}
}

function doEstimateShipping()
{
	fld = document.getElementById("zip_code");
	em = fld.value;
	box = document.getElementById("ship_estimate");
	box.innerHTML = '<img src="/images/ajax-loader.gif"/>';

	req = getXmlHttpRequestObject();

	if(req.readyState == 4 || req.readyState == 0)
	{
		url = '/estimate_shipping.php?zip=' + escape(em);
		req.open("GET", url , true);
		req.onreadystatechange = handleEstimateShippingResponse;
		req.send(null);
	}
}

function handleEstimateShippingResponse()
{
	if(req.readyState == 4)
	{
		box = document.getElementById("ship_estimate");
		message = req.responseText;

		if(message == '')
		{
			box.innerHTML = 'Invalid zip'
		}
		else
		{
			box.innerHTML = '<u>$' + message + '</u>';
		}
	}
}