We have a relatively new website (no external links, PR0, DA17) and we are making a major change in content. On the one hand we have to incorporate new content and otherwise eliminate much old content.
When we finally make this change, for several reasons, more than 100,000 URLs will give a
404 error. The main reason is that the URL pattern of products will change from something like
How would you recommend to proceed in order to minimize page not found errors?
In most cases, we will do a
301 redirect. But we do not want to abuse these redirects.
So far we are blocking
404 pages using
robots.txt and manually de-indexing many from Webmaster tools, as explained by Google here.
Would you launch the site with this big amount of 404 errors, hoping that they will gradually disappear, or would you clean them in any other way?