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Hi There Generally those types of 404's won't be too harmful - they sound like they may have been somewhat artificial WordPress pages. What I would do is get your list now from Analytics or Webmaster Tools - this way you will capture URLs that actually got traffic or Impression in Google and redirect those. So run a landing pages report, and an top pages report in webmaster tools - maybe for the last 6 months. Create a text file of all the URLs, and run them in list mode through Screaming Frog. Redirect any that 404. If you were to go back in time, what I would have done with Screaming Frog is - let it crawl everything - you have to allow it to "follow redirects" and "ignore robots.txt" etc - I know Google is not supposed to crawl anything in robots.txt - but basically you'd be letting Screaming Frog get to everything, that way you don't miss any URLs.

Howdy, Great question. A couple of metrics that I like to focus on are "# of unique linking root domains" to a site, and also overall Domain Authority and Moz Trust. It's not really about the pure number of links. Even a spam blog can generate millions of backlinks without moving the rankings. Instead, it's more about the breadth, quality, trust and topical relevance of the sites linking to you. If there's one metric that most agencies use for benchmarking, it's Domain Authority, but I'd be careful with this as it can fluctuate from month-to-month and should be thought of in broad terms instead of as a precise number that you track from week to week. I think this blog post by Dr. Pete perfectly answers your question better than I could myself. It's well worth a read. http://moz.com/blog/whats-better-on-page-seo-or-link-building Let us know if you have any questions. Best of luck with your SEO!