i have 2 sites. one having name myurl.com & another is myurl1.com, myurl having PR 5 & myurl having PR 0. i got many backlinks from myurl.com & no backlinks from myurl1.com, if i redirect myurl1.com to myurl.com then does my PR (myurl.com PR 5) affected? does it mean both domains are working? so can i do link building for both domains? or redirect mysite1.com to mysite.com & do linkbuilding for myurl.com. what this technique called? is that a part of BLACK HAT SEO??
Your pr for myurl.com will not be affected, if you are going to redirect you should use 301 redirect, this is a white hat seo technique. Both urls will work but there is no need to build backlinks to both urls you should only build backlinks to the main url myurl.com.
hmmmm... i had a similar situation about a year ago.. i had mysite.com (fake domain) (PR4) forwarding to a blogspot.com blog (PR2) when i created a wordpress blog on the mysite.com (PR4) and stopped the forwarding to the blogspot.com blog (PR2) mysite.com DROPPED to a (PR 0) when the Google PR updates came around... however my blogspot.com blog still remained a PR 2 it was the weirdest thing.. but i must say it's taken a bit but mysite.com has since then jumped back up to a PR3 the last PR update so eventually it will work itself out within the system...