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Howdy, Unfortunate, it's really hard to asses why you may have experienced a drop without a deep-dive look into your site, links, and history. But there are some basic steps you can take to help diagnose the problem. 1. Check Google Webmaster Tools for any messages, HTML suggestions, crawling errors or other indications of problems. Sounds like you might already be doing this. 2. Check the date of your drop against known algorythm updates. The Google Algo History is a good place to start. 3. Do a complete site audit. Here's a good template for one: http://moz.com/blog/how-to-perform-the-worlds-greatest-seo-audit 4. Completely crawl your site using a tool like Moz or Screaming Frog, looking for common errors. 5. Check your backlink profile for dodgy links. Paddy Moogan wrote a good guide on how to do this: http://www.stateofsearch.com/step-by-step-guide-finding-low-quality-links/ The key here is to try to identify any problems that you can fix. Sometimes Google simply changes the way they rank sites and devalues your link profile, your content, or something else that's hard to control. But once you identify the problem, it's much easier to fix.