Abstract : Nowadays, mass customization has been embraced by a large portion of the industry. As a result, the web abounds with sales config- urators that help customers tailor all kinds of goods and services to their specific needs. In many cases, configurators have become the sin- gle entry point for placing customer orders. As such, they are strategic components of companies' information systems and must meet stringent reliability, usability and evolvability requirements. However, the state of the art lacks guidelines and tools for efficiently engineering web sales configurators. To tackle this problem, empirical data on current practice is required. The first part of this paper reports on a systematic study of 111 web sales configurators along three essential dimensions: rendering of configuration options, constraint handling, and configuration process support. Based on this, the second part highlights good and bad prac- tices in engineering web sales configurator. The reported quantitative and qualitative results open avenues for the elaboration of methodolo- gies to (re-)engineer web sales configurators.