The current paper tackles the issue of determining a method for estimating maintenance costs for web applications. The current state of research in the field of web application maintenance is summarized and leading theories and results are highlighted. The cost of web maintenance is determined by the number of man-hours invested in maintenance tasks. Web maintenance tasks are categorized into content maintenance and technical maintenance. Research is centered on analyzing technical maintenance tasks. The research hypothesis is formulated on the assumption that the number of man-hours invested in maintenance tasks can be assessed based on the web application’s user interaction level, complexity and content update effort. Data regarding the costs of maintenance tasks is collected from 24 maintenance projects implemented by a web development company that tackles a wide area of web applications. Homogeneity and diversity of collected data is submitted for debate by presenting a sample of the data and depicting the overall size and comprehensive nature of the entire dataset. A set of metrics dedicated to estimating maintenance costs in web applications is defined based on conclusions formulated by analyzing the collected data and the theories and practices dominating the current state of research. Metrics are validated with regards to the initial research hypothesis. Research hypothesis are validated and conclusions are formulated on the topic of estimating the maintenance cost of web applications. The limits of the research process which represented the basis for the current paper are enunciated. Future research topics are submitted for debate.