Kristina - thanks for the feedback.

By any chance, would you have a site migration guideline that you recommend?

It is a problem with the site migration.

Never the less, I have a site right now with over 100,000 errors dealing with 404.

I'm looking for a game plan on how to deal with this many 404 errors in a time effective way.

Any ideas with type of tools or shortcuts? Has anyone else had to deal with a similar issue?

The WMT notion helps. Thank you.

The main concern is really timing. Are there any effective ways of going through thousands of 404 pages and finding valuable redirects?

I recently been given a site that has over one-hundred thousand 404 error codes listed in Google Webmasters.

It is really odd because according to Google Webmasters, the pages that are linking to these 404 pages are also pages that no longer exist (they are 404 pages themselves).

These errors were a result of site migration that had occurred.

Appreciate any input on how one might go about auditing and repairing large amounts of 404 errors.

Thank you.

In what type of a situation is it the best type of practice to use a self referencing rel "canonical" tag?

Are there particular practices to be cautious of when using a self referencing  rel "canonical" tag?

I see this practice used mainly with larger websites but I can't find any information that really explains when is a good time to make use of this practice for SEO purposes.

Appreciate all feedback.

Thank you in advance.