When using a formula like =HttpHeader("http://"&A2&"/","Server"), where A2 is a domain name, when trying to apply this to a large list (thousands) of domains, a large percentage of the responses are ArgumentExceptions. If I drag the formula down 28 rows, none return an ArgumentException, when I drag it down 29, one of the rows will return ArgumentException. (though it isn't the last row)
Using Excel 2013 32bit and seotools 7.0.8.