Web systems are based on client-server architecture wherein a client typically enables users to communicate with the server. Therefore, these systems share some characteristics of client-server architecture. However, there are a number of aspects of web systems that necessitate having different techniques to test them. These are discussed below,

1. Clients of the traditional client-server systems are platform-specific. This means that a client application is developed and tested for each supported client operating system. But the web client is operating within the web browser's environment. Web browsers already consist of operating system-specific client software running on a client computer. But these browses need to support HTML as well as active contents to display web page information. For this purpose, browser vendors must create rendering engines and interpreters to translate and format HTML contents. In making these software components, various browsers and their releases introduce incompatibility issues.

2. Web-based systems have a more dynamic environment as compared to traditional client-server systems. In client-server systems, the roles of the clients and servers and their interactions and are predefined and static as compared to web applications where client-side programs and contents may be generated dynamically. Moreover, the environment for web applications, is not predefined and is changing dynamically, that is, hardware and software are changing, configuration are ever-changing, etc. Web applications often are affected by these factors that may cause incompatibility and interoperability issues.

3. In the traditional client-server systems, the normal flow of control is not affected by the user. But in web applications, users can break the normal control for example, users can press the back or refresh button in the web browser.
4. Due to the dynamic environment, web systems demand more frequent maintenance.
5. The user profile for web systems is very diverse as compared to client-server systems. Therefore, the load on web access due to this diversity is not predictable.