The Internet has penetrated our lives, becoming an indispensable tool for social, business and personal growth. Thanks to the Web, users can easily carry out many tasks that were previously difficult. Differently-abled persons need to have the same opportunities as everyone else, so accessibility and usability must be included in the design of all Web resources, applications and services. To be extensively applicable, accessibility and usability guidelines should be delivered as simple design features. In previous studies some conceptual frameworks have been introduced with this aim. However, the specific applicative environment such as trustworthy e-commerce services, may offer ad hoc challenges. In this paper, we propose some guidelines to extend the design of usability conceptual frameworks in order to promote trust in e-commerce websites for people with visual disabilities.