If I add link of PR4, is that affect the pagerank of your site.

If I add link of PR4, is that affect the pagerank of your site. Is google consider it in evaluating the backlink of the site?

 

Your PR won't reduce because of that link. They might get some PR the amount of which depends on the number of OBL's you have on your page.

Just ensure that you are not linking to ''bad neighbourhoods'' That might result in some kind of penalty and can affect your rankings for your keywords.

 

what/who exactly qualifies as "bad neighborhood"?

 

Spam sites, porn sites, just sites you wouldn't want linking to you

 

also be aware of link farms as well