I just find this interesting article about SEO. What do you think? Is it true that there is no such relevant links, or every link is basically relevant?

I think it all depends on the search engine since they all do things differently. Doing one thing may get you a high rank in Google, whereas it would have little to no effect in Bing and vice-versa.

I get a headache thinking about SEO.

Check the date on that article - June 2007. Many things have changed in the world of SEO in 3 years (heck in 3 months).

I would not base a campaign on the information listed in that article. Relevant links DO play a role in SEO, and even more important, relevant "do follow" links play an even bigger role.

When looking for how to do something, please be sure to check dates on the articles. Things from last year and 2 years ago can be very different. It's one of the things I don't like about search engines showing results from 1998 sometimes. There's still articles out there that say there's nothing better than HTML Tables for quick page loading times. Others that say use a DIV tag, and then others (more recent) that say use CSS. The date of an article should play a big role in your research.

Wow, thanks Connor for the advice, I didn't notice the posting date before. I agree with you. SEO techniques are ever changing and you cannot expect things to stay the same after 3 months, let alone 3 years. Just curious, when did SEO expert at the first time suggest that there are relevant and non relevant links?

Relevancy issues have been addressed since the Internet's inception. The methodology and value assigned to links has evolved over the years.

i think the stronger relevancy comes into play only for very competitive keywords/subjects (hosting is one of them)

but for not as competitive topics, relevancy is less important and title/words and a few links should do it