Quality indicators for Google SEO

I’m looking to push some of my own sites more seriously, in terms of adding value and raising traffic.

Here’s some of the potential quality indicators that can be used for Google rankings:

1. Unique IP
2. SSL cert
3. Privacy policy
4. Full contact details - email, postal, & phone
5. 10 year domain registration
6. robots.txt
7. W3C validation

It’s fair to say most of my sites have none of these features, but I push for them on my most important sites.

Of course, there’s no guarantee that adding potential quality indicators will actually help a site rank better - but if the site is important enough, it’s worth making that extra effort to leverage any and all advantages you can from the content side.

UPDATE: Added 6 & &. :)