Robert_Charlton - 2:38 am on Apr 18, 2013 (gmt 0)
To add to Whitey's post, you need to be a paid Supporter to qualify for the review. IMO, it's a bargain. I've seen these reviews help some sites a lot (when site owners follow up and fix their sites).
Have you made changes to the site before or after the ranking change?
Yes, important consideration. Also check whether someone is duping your content. Search for, say, 4 or 5-word unique text strings (in quotes) and see whether it's appearing on other sites. Don't just try one phrase... try several, case the text is broken up on sites that might be scraping you.
where can find the quality of your links
This is a long discussion that I'll let others flesh out. Quick answer is that Google wants "freely given, editorial links". Links you place yourself, profile links, free-for-all directory links, etc, are liable to be hurting you more than helping.