Obtaining a performance metric in a system for conveying web content from a server node to a terminal node along one or more network nodes, involving an inspecting of a data flow transmitting said web content toward the terminal node for extracting web content records. The extracted web content records are correlated to at least one web session. The extracted web content records are associated to a performance of one or more of said nodes. The performance metric is calculated from the correlated and associated web content records for at least one web session and one or more of said nodes.