In this paper, we aim at providing conceptual and empirical insights to the design of security indicators in web browsers. In examining why security indicators in web browsers fail to warn users about web frauds, we propose affordance-based principles for our new design of web authentication indicators. Following these principles, we present a new design for Extended Validation (EV) certificate interface in the Firefox browser. We then conduct an exploratory qualitative study to evaluate three different versions of EV indicators. Our findings offer some preliminary implications for the designs of more effective web authentication indicators.