In addition to download time, network capabilities can affect a Web server's resources. Slow networks require Web servers to keep HTTP connections open for a longer time, tying up resources. Unreliable networks at the user end can require repeated attempts to send packets and eventually cause dropped sessions. Unless handled properly, such dropped sessions can cause problems with system resources and locked data. For example, a user's session may be dropped in one tier of the architecture but not another, locking the user out of the data until this second tier resets the lock and reinstates the user access.
Networks are heterogeneous, and so are user configurations.
In addition to these considerations, you must also consider the possibility of various Web appliances such as WebTV, I-Opener, or PDAs. With the many possible permutations between these dimensions, the issue of client compatibility becomes very thorny and can often be overwhelming. The first step in minimizing site problems is to be extremely clear about your target audience and the client configurations you will support. Any variation could cause problems. Although the possibility that Netscape version 4.75 with Flash 4 running on Windows 98 will work fine while the same version running under NT will produce an error may seem unusual, such errors do occur.