Andy_Langton - 9:15 pm on Apr 4, 2012 (gmt 0)
Remember that while it's keywords that drive traffic, it's the landing pages that facilitate that so looking at landing pages is usually better than looking at keywords. For ranking drops (and if your analytics allows it) I would start looking at:
- Landing page
- Keywords for those pages
It's also worth a check in Webmaster Tools for CTR/rankings, and your own ranking data/CTR calculations if the data's there.