High resource availability in computer networks has become a critical issue as it can be affected by the increasing number of network users. A methodology based on classifying website visitors into priority groups is proposed, assuring high availability for priority classes, based on reserved website resources that can be accessed only by these groups and simultaneously providing as many resources as possible to lower priority visitors. A birth-death process is proposed to model website visitors? arrival and service. An optimization problem is solved to determine the optimal trade off between resource availability for high priority visitors and free resource access to lower priority visitors. The major contribution of this paper consists in deriving formulas for the probability that a website visitor has no further access to resources and in determining the optimal reserved resources assuring the above trade off.