1. JavaScript is a programming language built into web browsers that allows for source code, algorithms, and input/output of data. Variants include ActionScript and JScript. 2. jQuery is a JavaScript library that makes complex tasks easier by providing functions to simplify things like DOM manipulation. 3. Debugging tools built into browsers can help proofread markup languages for errors by catching problems as the page loads. While coding standards help, computers don't always behave predictably so issues may still occur.