How to prevent cross-site scripting security issues

How to prevent cross-site scripting security issues: "Dynamically generated HTML pages can introduce security risks if inputs are not validated either on the way in or on the way out. Malicious script can be embedded within input that is submitted to Web pages and appear to browsers as originating from a trusted source. This problem is referred to as a cross-site scripting security issue. This article discusses cross-site scripting security issues, the ramifications, and prevention."