This is really a helpful for webmaster and website owner to remove unwanted web pages or accidentally make private web pages live which is now cached by search engines. If you have verified your ownership of website in Google Webmaster Tool and want to remove unwanted URL then now you don’t need to block such pages before requesting URL removal.
Removal Request Persist for 90 Days Period
When a URL submitted for removal in Google Webmaster Tool, Google consider it as a temporary removal request and continue crawling for 90 days period. In this 90 days period Google will crawl pages but not display in their search results. At any time during this 90 days period you can cancel removal request. After 90 days the pages submitted for removal can reappear in search results. So, this is helpful if by mistake you have uploaded some personal data that you don’t want Google to crawl.
Permanent Removal Request
If you wish to remove your website content permanently from Google search results then you must block your webpage using following blocking parameters:
1. Make sure that the page no longer exists by returning 404 or 410 HTTP Status code.
2. Block such page using robots.txt file.
3. Add no-index meta tags in page you want to remove.
Google interpret this as a permanent removal request and remove page permanently from their search engine till any of the following blocking parameters present on the page. If you in future you remove blocking parameter Google may crawl the page again and start popping up in their search result.