As far as SEO(Search Engine Optimization) is concerned, Links are Very Important Factor for Taking a website to High Rank On Search Engine like Google, Yahoo, Bing..at the other end link relevancy also plays a crucial role for getting high ranking to your website, also keep in mind that it should not be reciprocal.

Recently Google webmaster updated for quality link:- To Have a Quality links we need to take care of link relevancy and submissions should be on High PR websites as Do-follow high PR link is vital important for organic searching.

The numerical analysis of Quality Link says:

Quality link = PR+DO-follow + relevant +Exiting link
Here PR is considered as High Page Rank websites, PR can be 1, 2, 3 upto 10.
Do-follow links are crawled by the spider or crawler.
Existing link:- That means Link should be Permanent not for a limited time.

Lets have a look on SEO Site Advice from Experts: