I have deleted a couple of thousand pages from a website. They do not appear in my sitemap.xml and no other pages on the web are pointing to these anymore. Google Webmaster Tools (GWT)'s crawl error pages starts to report them as not found. There is an option to mark them as fixed. Should I mark them as fixed? They are not really fixed and won't ever be fixed.There is also a remove URLs page, but there is no way I will manually remove those pages one by one (REM: those pages are not in a single directory, they were all over the place, so there is no robots.txt directive I could use).If Google does not find a page, does it automatically remove it from its index, or if we mark it as fixed, does it try to reach it over and over again?
Should I 'mark as fixed' deleted pages in Google Webmaster Tools?
google search console;google index
Whether or not you mark them fixed will have no bearing on your site performance. The idea of that feature is just to allow webmasters to clean up their report when they have fixed errors. Google will eventually get the idea that a page isn't coming back, but it can take a while. Arguably, if these pages are gone forever they should return a 410 HTTP code. Apparently there's not much difference in how Google treat 410s and 404s, but John Mueller from Google has suggested that 410s may get cleaned up more quickly.Alternatively, depending on what you've deleted and why, there may be a good user experience argument to 301 redirect to some near equivalent (say, a parent category landing page). That can have SEO advantages, too.