Meta tag query

I think I have read that there is a meta tag that can be used on a site
while under construction that will prevent it from being logged by any of
the search engines. If so, can someone tell me what it is?
Would it need to be in every page or just the root directory index page?

Thanks
Brian Tozer

Thanks very much Brucie.
Very helpful answer as usual
Brian.

"brucie" <shit (AT) usenetshit (DOT) info> wrote