1. A network device, comprising: a transceiver to send and receive data over a network; and a processor that is operative to perform actions, including: determining a plurality of document features for each document in a plurality of documents, wherein the plurality of documents include at least one document defined as having sufficient subject matter specificity, and at least one other document having insufficient subject matter specificity; training a document classifier based at least on the plurality of document features including at least a frequency of visual line breaks and a frequency of images for the at least one document having sufficient subject matter specificity; providing to the trained document classifier, the at least one other document, wherein the trained document classifier determines a first quality value for the at least one other document; if the first determined quality value of the at least one other document is above a quality threshold value, identifying the at least one other document to have sufficient subject matter specificity, and providing the at least one other document to a client device for display; if the first determined quality value of the at least one other document is at an unacceptable level, re-training the document classifier based on at least the plurality of features for the at least one other document; and if a second quality value of the at least one other document is determined by the retrained document classifier to be above the quality threshold, providing the at least one other document to the client device for display.