What happens if the blog you commented in is a "no follow" blog site? What effect will it have in SEO building? How do you determine if a blog you want to comment in is "do follow"?
How many links (external) do you have to put on your web page before Google start to treat your web site as a source of spam?
What is the worst thing and the best thing you can do when you are building links to your site in order to promote it?