How to fix massive 404 pages?

Are there any real pages or they are non-existent?

best to convert that pages to 410 status code so that google will delete automatically once its get 410

Just use a redirect code and send those 404 pages to main page.

Makarand's answer is a very good one and is pretty comprehensive. I'd definitely check that article out. I'd also recommend reading "Is Your WordPress 404 Page Killing Traffic & Drinking Your SEO Juice?" as it has some specific recommendations for plugins to help you out depending on what you are trying to accomplish.

How is it that you have 9k worth of 404s on wordpress? Is it related to a change in your permalink structure? If so, you may want to check out the Change Permalink Helper plugin.

I find myself using WordPress › 404-error-monitor " WordPress Plugins to easily determine which links are generating the most 404 errors, and then I use Safe Redirect Manager to create 301 permanent redirects for the most common 404 links to point them to a page on my site that seems relevant (based upon the structure of the link that is producing the 404, which will only be helpful if you are using Pretty Permalinks, which you should always be using btw).

Hope that helped. Good luck - that's an awful lot of 404s!

Ungagged SEO team,London