mcskoufis - 5:50 pm on Jul 10, 2013 (gmt 0)
To monitor the health of a website, I would start with search referrals. It does not matter if you rank #1 for a search term, if that search term brings in no traffic. I would want to see steady growth in Google traffic and conversions from that traffic. When traffic goes down, I would then look in analytics to try to identify specific search terms that are underperforming, then I would look at rankings.
+1 @ GoodROI
It all comes down to specific business goals. After all the client is expected to invest both in SEO and on improving the website (content, coding, multimedia, etc.)
We need to educate the clients that SEO is measured by specific business goals. Sales, leads if there are no direct sales, newsletter sign-ups etc. Metrics such as Google Toolbar PageRank can only be an indicator which makes no sense to many people, as they won't even know that it is an exponential metric and not linear (please correct me if exponential is not the right word).
People do get confused heavily, especially those in corporate marketing departments ;-)