So, we've had this sudden traffic drop on 4-5 September and we are now at 50% of our regular traffic. I've been researching about the causes of the issue and unfortunately, I'm totally stuck, with no clear way to deal with recovery. I'd therefore appreciate your feedback and suggestions.
1. I removed large number of unwanted tags from our site in August. All these tags resulted into 404 errors.
2. Sometime around beginning of September, the Disqus plugin on our site resulted into invalid URLs being formed. So our 404 error count, as reported by Google Webmaster Tools rapidly went from 1k errors to 17k to 44k to 70k to 99k.
4. On 5th of September GWT reported sudden rise in Page Not Found Errors. And on 4th of September we had began noticing that our traffic wasn't what it should be.
I concluded that it's the large number of errors causing Google to drop our site in rankings and fixed those errors around October 15. Now almost all the errors causing 404 errors have been fixed.
Google continues to say that 404 errors don't affect website rankings and I've made sure that nothing on our website would really get affected by Panda, Penguin or PLA algorithm (there was no algorithm update on 4-5 September). Now the low value pages are outranking us for several of the keywords that were #1 for several months (years). We only followed basic SEO rules; never over-optimised or did any black-hat SEO.
Since 15 of October (after fixing the errors), I'm noticing that the GWT drops 1000 errors/day (which I mark as fixed) and saw some positive trend in search queries.
The GWT still shows 88k 'Page Not Found' errors (I've fixed all them already) and continues to drop them from the reports at the rate of 1000 per day. But if it's not the large number of errors causing the drop; what are the steps I should take to recover from the traffic drop? I need to be sure about my recovery strategy. I'd welcome your suggestions.