That’s a good question, and even seasoned webmasters from way back in the early 90’s think the easiest way to fix the issue is to simply remove the page. Why remove the page? It’s just as easy to type a question in Google, and get a response back, have the page removed.

You have several options in this case, since you have a page that you don’t want in Google.

1. Use a robots.txt
2. Use Google’s EXCELLENT webmaster tool
You are not a webmaster if you don’t use this tool, don’t even use the title of webmaster if you don’t.
3. Delete the page (The easy excuse way of dealing with it)
4. Rename the page (See above thought, although not so bonehead)
5. Password protect it (Which can be defeated in some ways)

Password protect is the best option there is, since in most cases I believe Google won’t index a page that pops up a standard auth windows. (The really smart way to do it, and it only take less than 10 seconds to do in Unix and Windows.) This option is immediate, while not perfect.

Using robots.txt is a great option, however there is a caveat. Some people think that since Google doesn’t spider often, they are at no worries they’ll find the new URL of the page they moved it to. This is the flat out, ignoring advice thing to assume. Even in the light of being told that Google can, and does spider sites very quickly, is adding new datacenters and refreshing the index much more often. Hell, it may even break and ignore what you type into robots.txt.

If your webmaster assumes this, run and don’t look back. They lack understanding to put anything online because they refuse to understand what information leaks are, and the dangers of saying they don’t have enough time to write a 10 second robots.txt. This is all conjecture, due to that fact that for some sites, Google has a really slow crawl scheduled. Meaning: they don’t update content, or it’s unimportant so Google doesn’t care.

Using robots.txt in this case, without knowing how long it is that Google hits your robots.txt could mean that the page affected will remain for over months. Google won’t even attempt to remove it in the next index refresh until they see that robots.txt.

The best option is to simply do what the other webmasters of the world do: Use the webmaster tool that Google provides, take the 5 minutes to see what it does, and be what you claim to provide. Request the url to be removed using the webmaster tool and you will find that quickly it’s gone.