Tate. One way is to create a simple page on the site that returns a specific word when the URL is visited (tCheckURL). Then you can;
put URL tCheckURL into tContent
if tContent = "Online" then
...
end if
In the example above, the URL should only return the word "Online", so if you receive anything else instead (blank, ISP error, etc...), you know that access to the site is temporarily down.