This method uses the HEAD command to retrieve header information
about the file without downloading the contents of the file itself.
This requires that the server support at least version 1.0 of the
protocol standard, or an error will be returned.
The server may not return a modification time for some
resources. If the request to the server was successful and the file
exists, but the server does not return a modification time, the
method will return an empty string.
When a request is made to the server for information about the
file, the control will attempt to keep the connection alive, even
if the KeepAlive property has not been set to True. This
allows an application to request the modification time and then
download the file without having to write additional code to
re-establish the connection. However, it is possible that the
attempt to keep the connection open will fail. In that case, an
error will be returned and the session will no longer be valid. If
this happens, the method may still return a valid date and time. To
determine if an error occurred, check the value of the
LastError property.
The Localize property will determine if the returned file
time is adjusted for the local timezone.