Target volume delineation is a critical, but time-consuming step in the creation of radiation therapy plans used in the treatment of many types of cancer. However, variability in target volume definitions can introduce substantial differences in resulting doses to tumors and critical structures. We developed TaCTICS, a web-based educational training software application targeted towards non-expert users. We report on a small, prospective study to evaluate the utility of this online tool in improving conformance of regions-of-interest (ROIs) with a reference set. Eight residents contoured a set of structures for a head-and-neck cancer case. Subsequently, they were provided access to TaCTICS as well as contouring atlases to allow evaluation of their contours in reference to other users as well as reference ROIs. The residents then contoured a second case using these resources. Volume overlap metrics between the users showed a substantial improvement following the intervention. Additionally, 66% of users reported that they found TaCTICS to be a useful educational tool and all participants reported they would like to use TaCTICS to track their contouring skills over the course of their residency.