There are times when we would like Google and other search engines to completely remove a URL from search engine results. These would be incidents like accidentally leaving personal information on the web page or website being bombarded with spammers, etc. In these critical moments, webmasters can take several actions to remove the URL of a page but with so many alternatives, it sometimes becomes difficult to ascertain that your chosen method is the most viable option. Matt Cutts, in his explanation, provided very lucid information in this video which I thought needs sharing.
There are primarily six methods used by webmasters to remove a URL from SERP but, ironically only two of them are foolproof.
Highly Recommended Methods
In order to stop robots or anyone else accessing the URL, you can password protect the sub directory containing that page. A robot cannot guess the password therefore doing so will make it virtually impossible to access.
2. URL Removal Tool
This tool is available on the Google webmaster toolbar so you can request Google not to index the URL. Furthermore you can remove the entire domain, sub directory or individual URL. A possible drawback is that sometimes it takes a couple of days to complete the request.
You can disallow robots from accessing the intended URL by placing the robot.txt file in your server root. The only problem with this method is that Google and other search engines can still track the URL if someone else has placed a link to your page. There are other loopholes too. Learn more about robots.txt here.
Using noindex Meta Tag is an easy and powerful technique to stop web crawlers from accessing the URL but it will only hold Googlebot at bay. Even with noindex tag, Microsoft and Yahoo crawlers will still show a reference of URL.
Least Recommended Methods
Using nofollow on individual links is a weak approach. If someone else has linked to your URL, then search engines will be able to find that URL.
6. No Links to a Page
If you are assuming that non of the other webmasters have ever linked to your ‘not so visible’ page and it mostly lay dormant then think again because someone surfing that particular page may have unknowingly referred the URL to another server thus making it visible in the SERP. Therefore you should never leave a low profile web page unattended.