Kimkia - 7:12 pm on Jan 2, 2013 (gmt 0)

Hopefully, you have link rel="canonical" href="http://www.example.com/categoryname/"

Well, I confess what I currently have is:
link rel="canonical" href="http://www.example.com/categoryname/index.shtml"

with this in htaccess:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^example\.com
RewriteRule ^(.*)$ http://www.example.com/$1 [R=permanent,L]

When linking to the home page of each directory within my site, I always use the full url with the index.shtml extension - with one exception, which is a breadcrumb script that automatically links to http://www.example.com/categoryname/

I think this has lead to some dilution of page importance in Google, but I'm not sure. I just know my 11 year old site is suffering badly after years of doing very well. Is dropping the index.shtml extension recommended for SEO?

If so, then I assume that I need to 1) rewrite all internal links to the new format and 2) change the htaccess to the code cited above. Are there any other steps I should take?