The Web is a dynamic place. New versions of browsers (also known as clients or user agents) come out fairly often, and they usually include features that are not supported in other browsers or in earlier versions of the same browser. Some of these features do not work on every operating system (also known as an OS or a platform). This is because a feature might take advantage of built-in capabilities offered by one particular OS, or it might not be cost-effective in time, money, and effort to program for multiple platforms. In some cases, browsers are designed for special purposes and intentionally do not support features commonly supported by other browsers.
This chapter covers some general techniques for making your Web site accessible to multiple browsers. We will first cover some of the major differences among browsers; then we will examine some ways to make content more compatible across browsers; and finally we will explore some common problem areas in cross browser functionality and their solutions.