I have used so many things like url removal request and deleted the pages etc., but still the errors are shown in my webmaster tools.
How can I remove the urls completely from Google?
The short answer in the context of being practical: you can't.
What you can do is remove links that point to them and make sure that the pages respond with a 404 status code, and when Google sees that the pages are no longer in existence they'll eventually purge them from results.
In general, you can't. But there are some options.
One option is to remove the pages from your server entirely, and make sure they respond with 404 errors.
Another is to use the
robots.txt file to prevent Google from crawling the content. This will certainly prevent new pages from being indexed, but it may take a while for existing pages to no longer show up.
A final option is to use the
noindex meta tag.
For details, see Google's page on this topic: http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=164734
You can: Remove a page or site from Google's search results, but it will take a while before it takes affect.
There are two way to Remove URLs from Google Search Engine
If you don't want crawl your page in google, so you have to use google webmaster tool's Removal URL tool to request its removal Here it is the way
after few day your url will be delet from search engine and not able to crawl.
If your site has content you don't want Google or other search engines to access, use a robots.txt and disallow the folder of that web page.
you can use one of the above step to Remove URLs from Google Search Engine
If your site has pages indexed in Gooogle that you want to remove the first step is to change your site. You can either remove the pages or include a tag in them that tells Google not to index them.
<meta name="robots" content="noindex">in the
<head>section. Google will remove it from the index the next time it crawls it.
Disallow in robots.txt -- You can block Googlebot from crawling pages by adding
Disallow: /mypage in robots.txt. Google doesn't usually index pages it can't crawl and it never indexes their content. However, Google sometimes may show the URL in the search results without any snippet:
With all these methods, Googlebot has to return and crawl the pages before they get removed. This process may take a couple months, especially for many pages that are not very popular. If you want to speed the process up, log into Google Search Console and use the Fetch as Google feature for each URL. Note that this is a manual process with a quota of ten fetches per day, so it won't work for a large number of URLs.
Google also has a Remove URLs tool in Search Console that can temporarily remove URLs or directories from Google for 90 days. You can use this tool to remove URLs from search results quickly before Googlebot has a chance to crawl them.