It's the common misconceptions that it seems a lot of people have about SEO. Based on my own testing, here is what I have discovered:
NoFollow links are bad
False. No Follow links are actually good. When used correctly they can actually boost your rankings. This is because search engines see that your linking strategies are natural and it doesn't seem as though you are forcefully getting links back to your pages.
When people click through nofollow links and land on your page, search engines recognize this. They KNOW where your traffic comes from, and give you points for quality visits (ie; time spent on your site)
Google Penalizes Duplicate Content
Believe it or not, FALSE. Well, true and false. If you have the same content as somebody else ranking for a certain keyword Google will not allow you to rank highly for that particular keyword.
HOWEVER, in my experience, it is completely possible to rank the same content highly for a different keyword.
Topic Related Backlinks Aren't Important Anymore
Big fat false. The search engines love topic related posts. Besides the fact that the algorithms seem to lean preferably towards topic-related backlinks, the fact is that when you have a link from a PR5 cooking website to your dog grooming website you will naturally receive less traffic through your link than other relative links on that page. Therefore the search engines will learn over time that visitors don't like your links as much as other peoples links. -This does not look good.
I'm sure I have come across other misconceptions like these but these are the ones I just had to get off my chest.
If you have any SEO-related questions, feel free to drop me a personal message or email (dave@SEOJuice.net)
All the best,