Amnesty International on Sunday accused the world's Internet firms of colluding with repressive regimes to curtail online freedom. The human rights group launched a campaign against Internet censorship, singling out Yahoo, Microsoft and Google for complying with Internet censorship in China...Amnesty's online campaign, http://www.irrepressible.info, urges Internet users to sign a pledge for online freedom, and to include material which has been banned in states such as China, Syria, Iran and Vietnam on their Web sites.