httpwebrequest please help clarify

[seal]

I am posting an xml document using httpwebrequest post method using a
x509certificate, my question is this, is this secure if I am posting to an
http:// and not https://? Is this the correct way to go about this as opposed
to using a webservice maybe? Is my data that is being transmitted over the
web secure? I am using a certificate to log onto the website, therefore being
able to navigate to the proper page by the post method and processing the
xml, I am looking for the proper way to do this.

Thanks!