This paper discusses the use of the Efficient Turning Band (ETB) geostatistical simulation method to enhance web performance forecasting accuracy for distributed computer systems. The approach involves a spatio-temporal prediction framework that considers both geographical and temporal factors affecting web resource downloading times. Results indicate that the ETB method, compared to traditional methods, yields better accuracy in forecasting web performance, thereby aiding in the selection of optimal web servers and improving Quality of Service (QoS).