Link Popularity Explained

[mandy]

The importance of a web page is measured by in two ways, as detailed below:

1) Onsite Optimization
This form of optimization is commonly referred to as "search engine optimization"...
2) Offsite Optimization
This form of optimization is commonly referred to as "Link Building." It is often categorized under three identities called "one way links," "reciprocal links," and "text link advertising," as detailed below:...

full article: http://www.webpronews.com/expertarticles...ained.html

[jezebel]

"one way links," "reciprocal links," and "text link advertising,"

All 3 types of links can hurt  you too if you abuse them.