Internet Gopher development team. Working with other pioneers such as Tim Berners-Lee, Marc Andreessen, and others. McCahill was involved in creating and codifing the emerging standard for Uniform Resource Locators (URLs). In 1994-95 McCahill's team developed GopherVR, a 3D user interface for the Internet Gopher protocol to explore how spatial metaphors could be used to organize information and create social spaces. Mark was also one of the six principal architects of the Croquet project (along with Alan Kay and others). He is also the managing editor of The Alphaville Herald (formerly known as The Second Life Herald), a newspaper covering virtual worlds. Mark also teaches about virtual worlds at Duke University.