The Pages which in not on my sites n also in my sitemap show me in Goggle webmaster crawl error section as a not found error. Not getting exactly what happen how to overcome.
1) Look at the details to make sure you didn't typo a link somewhere in your site. If you did, fix it.
2) If the page doesn't exist and it's not an error you made, 301 redirect the url to the most appropriate page on your site.
Even I saw a couple of not found errors and I just redirected it to my homepage.After that I marked it as fixed in the webmasters account. Problem solved
Make sure to check your site once and also the links which are showing the "not found" error in your webmasters account to be 100% sure