This paper describes the design and evaluation of a Web Accessibility Information Resource (WebAIR) for supporting web developers to create and evaluate accessible websites. WebAIR was designed with web developers in mind, recognising their current working practices and acknowledging their existing understanding of web accessibility. We conducted an evaluation with 32 professional web developers in which they used either WebAIR or an existing accessibility information resource, the Web Content Accessibility Guidelines, to identify accessibility problems. The findings indicate that several design decisions made in relation to the language, organisation, and volume of WebAIR were effective in supporting web developers to undertake web accessibility evaluations.