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??