Mine

function makeHttpRequest(url, callback_function)
{
	var http_request = false;

	if (window.XMLHttpRequest)
	{
		http_request = new XMLHttpRequest();
	}
	else if (window.ActiveXObject)
	{
		try
		{
			http_request = new ActiveXObject('Msxml2.XMLHTTP');
		}
		catch (e)
		{
			try
			{
				http_request = new ActiveXObject('Microsoft.XMLHTTP');
			}
			catch (e)
			{

			}
        }
	}
	
	// If we can't create a connection to the server we'll return true.
	// We'll check it server side anyway, this is a feature, not a requirement. ;)
	if (!http_request)
	{
		return true;
	}

    http_request.onreadystatechange = function()
	{
		try
		{
			if (http_request.readyState == 4)
			{ 
				if (http_request.status == 200)
				{
					eval(callback_function + '(http_request.responseText)');
				}
				else
				{
					alert('There was a problem with the request.(Code: ' + http_request.status + ')');
				}
			}
		}
		catch (e)
		{
			
		}
	}

	http_request.open('GET', url, true);
	http_request.send(null);
}