An HTML form lets readers enter information in fields, choose items from a list, or specify a file to be uploaded, and then send their information to the Web server. HTML forms are commonly used to let readers join mailing lists, purchase products, request documents, and send feedback. QuarkXPress software and QuarkXPress Passport software make it easy to build sophisticated HTML forms. Once the data from the form reaches the server, it must be processed by a server-based script or application. Typically, such scripts and applications use the Common Gateway Interface (CGI) protocol and may be written in languages such as Perl, C, and Java. If you want to use HTML forms as part of your Web site, you'll need to use a third-party tool to build the server-end script or application.