Each Web browser is slightly different and shows Web pages in slightly different ways. Some are friendlier to certain Web languages than others, and so Web application development can be quite specialized.

A Web programmer must keep this variability in mind when designing Web pages. Some browsers are certainly more prevalent than others, and many programmers focus on such markets exclusively, figuring that their time will be well spent because their target audience is the majority anyway; however, especially with consumer-based websites, you never know where your next high-paying customer is going to come from and what browser he or she will use to try to view your Web page. Many practitioners of Web application development design pages using open source code or keep things simple in order to maximize the pages' exposure.

One of the most basic types of Web application development involves e-commerce sites. This is the kind of website you see when you shop online. Designers of these sites must anticipate all kinds of unusual customer behavior, as well as heavy traffic, while keeping the server and "shopping cart" up and running.

The ease of online shopping has created an "always-on" environment in which people can shop at all times of the day and night, wherever they are. E-commerce sites must be available to accept orders and money no matter what time it is at corporate headquarters. Web application development can lend itself specifically to e-commerce site creation, but the programmer would do well to keep the 24/7 mentality of potential customers in mind.

Another kind of Web application development is used for Web-based office applications. Many offices nowadays use the World Wide Web to conduct their business operations, including all manner of accounting and tracking functions. Conference calls via the Web are also popular, as are file transfers. Web application development for all of these practices is specific and in high demand.