1. A computer implemented method comprising: receiving a graph search query specifying user-selected graph search elements, each graph search element corresponding to one of a graph node or graph edge connecting graph nodes; generating graph search query metadata representing the graph search elements of the graph search query and relationships of the graph search elements of the graph search query; comparing the graph search query metadata to content metadata sets, wherein each content metadata set represents content elements of a content item presented on a respective web resource and relationships of the content elements; determining similarity scores between the content metadata sets and the graph search query metadata based on the comparison; and selecting one or more of the web resources on which the content items are presented based at least in part on the similarity scores of the respective content metadata sets.