Visa Inc. and Amazon.com Inc. announced an agreement Thursday that allows customers to use Visa cards on Amazon sites worldwide without additional fees. The companies also agreed to collaborate on product and technology initiatives for “innovative payment experiences,” Visa said in an email. Credit card fees have been a growing source of tension between Amazon and Visa. Last year, Amazon started charging customers in Australia and Singapore who use Visa credit cards a 0.5% surcharge. Under the agreement, Amazon’s amazon.co.uk site in Britain will no longer turn off Visa credit cards. Customers…