AJAX XMLHttpRequest Error Flag

Question

Hi,

I made a query to an address and I got the readyState = 4, and the status = 0. After I read the documentation for the XMLHttpRequest, it says if the status = 0 and readyState = 4, then check the associated error flag. How can I see whats in this error flag to determine the cause of the status not being set to 200?

Thanks.