Gumtee - 8:33 am on Oct 18, 2012 (gmt 0)
Thanks to this thread I think I'm closer to knowing what happened to one of my sites... After a remake to a more modern Magento e-commerce system, the site dropped from 1st to about 680 out of 700 for its main keywords. The site sells one type of curtain only, so most of the text and links refer to these 2 keywords (eg folding curtain and folding curtains (direct translation from dutch)).
In the last 6 months I have de-optimized, improved speed, fixed duplicate metatags (the whole webmaster tools tour), removed an hidden text help system (user clicks on question an sees answer) etc to no avail. Requested a re-submission, got the standard message that the site is not being manually penalized... It's just a standard e-commerce site that sells custom (folding) curtains, no affiliate links, no spam, domain is 4 years old.
If anyone has recovered from this, please share how you did it.