Hi, I'm a little confused with external links. Is it better to have external links to other related sites or not (booth high and low PR)? If it is better to have that links, can I have nofollow tag and get profit of that external links?
having lots of outbound links is not a good practice from the view of SEPR. Nofollow tag is interpreted by various search engines differently, read this article(Nofollow) to know more about nofollow tag and it's influence.
also you need to have strong inbound relevant links more than outbound links, than it will works for you, but don't try to external links on your website.
I have lots of strong inbound links. My page is PR5. Recently i removed external links from 10 000 pages (one per page) and noticed less visitors from google