Systems and methods for monitoring Web page content associated with processing a resource request are provided. A client computing device generates a sample image corresponding to a set of resources rendered in response to a resource request. A processing component, such as an image analysis component, then compares the sample image with an averaged reference image to identify a compared image. The averaged reference image is determined from averaging a pixel intensity value for each pixel in a first reference image with a pixel intensity value for each pixel in a second reference image. These first and second reference images both correspond to the same set of requested resources. The processing component then weights the compared image to produce a weighted compared image and determines whether a sum of the intensity values for each pixel in the weighted compared image exceeds a threshold. Aspects of systems and methods for generating an alert message if the threshold is exceeded are also provided.