Recognising if the website is down

[teju]

Hi all,
I have written a script which alerts on when the website is down.I have used XMLHTTP object and screen scraping the error and alerting it.But, sometimes it gives wrong alerts reason being the request to the page is not complete hence its sends alerts which are not true.Can any one tell me what would be the problem.Here is my code below
xml.Open "GET",x,true
Call xml.Send()
On Error Resume Next
If (responseState="Complete" and xml.Status<> 200) Then
send alerts

I dont understand why does it sends wrong alerts

Please, help me wth these.

Thanks