1)
Placing a link on your site back to google or another search engine : No
2)
Placing a link to W3.org : No, except maybe with a little hack (not tested)
3)
Adding a link to an email address : No
4)
Including form elements, such as drop downs, text boxes, etc. that include keywords : Keywords in form elements are considered as text (paragraph)
5) Having your entire site using CSS, instead of tables : It seems that no. I's now proven that Google don't care about W3C vlidation (
http://www.site-reference.com/articl...ogle-Care.html ). It might be the same for parting content & layout with full CSS coding. But it's much more better for code maintenance, accessibility and cross-platform compatibility.
6)
Including the DOCTYPE on the top of your pages : Don't have importance for Google, but for you & your visitors.
7)
Using a directory structure rather then pages : Yes, but it worth less than yesterday. Only MSN gives a high factor to keywords in URL.