This document discusses various tools for debugging and testing the web tier, including: - Firebug and Web Developer Toolbar which allow debugging of CSS, browser features, and JavaScript. - JsUnit which provides a unit testing framework for JavaScript with capabilities like test functions, suites, and automated testing. - Selenium which is a tool for acceptance testing that simulates user interactions and uses standard browser technologies. - Other tools mentioned are Crosscheck for unit testing, and tracing for viewing test outputs. The document emphasizes the importance of testing and debugging for software quality.