i have taken keyword link from commission junction for advertising on google adwords. google adwords say that i cannot write the link taken in ppc form. i need help from some one engaged in affiliate marketing via commission junction and posting ads on adwords. by not writing the code taken from advertiser how commission can be received.

You have to have a web site of your own before Google will accept you as an advertiser. Look at "Links." at the Google Learning Center http://www.google.com/adwords/learningcenter/
You cannot use the affiliate site that the Commission Junction's member company supplies to you. It has to be your own.