I 've tryed same site with different domain name. And the bit can go from 0,02 to 0,80 from the same ad and same keyword, just the domain name is changing. Does anyone know why so much importance.? Is this changing with time? software-cie.com
Well you need to have a relevant domain to the keyword that the user is searching. It will give you a better QS.
yes, domain names can help or hurt your quality score depending on if the keyword is in them ... if you are buying the keyword "dvds", and you have 2 domains onlinedvds.com and coffeehouse.com the former will be more relevant in google's eyes raising your quality score and lowering your minimum cost per click