Google Webmaster tools today eliminated the requirement that the webpage's URL must first be blocked by a site owner before the page can be removed from Google's search results. Google says "because you've already verified ownership of the site, we can eliminate this requirement to make it easier for you, as the site owner, to remove unwanted pages (e.g. pages accidentally made public) from Google's search results."
- Removals persist for at least 90 days
"When a page's URL is requested for removal, the request is temporary and persists for at least 90 days. We may continue to crawl the page during the 90-day period but we'll not display it in the search results. You can still revoke the removal request at any time during those 90 days. After the 90-day period, the page can reappear in our search results, assuming you haven't made any other changes that could impact the page's availability," explained Google.
- Permanent removal
"You must ensure that one of the following page blocking methods is implemented for the URL of the page that you want removed:
- indicate that the page no longer exists by returning a 404 or 410 HTTP status code
- block the page from crawling via a robots.txt file
- block the page from indexing via a noindex meta tag
This ensure that the page is permanently removed from Google's search results for as long as the page is blocked. If at any time in the future you remove the previously implemented page blocking method, we may potentially re-crawl and index the page. For immediate and permanent removal, you can request that a page be removed using the Remove URL tool and then permanently block the page's URL before the 90-day expiration of the removal request," Google said.
[Source: Google Webmaster Central blog]