working. In the Inspector tab there are three columns. From left to right: The HTML tree shows the document nodes. This allows you to see, add, or modify attributes by double-clicking on the tag name or attribute here. It can also be used to run JavaScript code directly on the website, for example, changing the document content or reloading the page: Support for DevTools features is still a work in progress, and it it can break in future versions of Firefox if there are changes to the messaging protocol. document.write("Hello, Servo!") location.reload() ⓘDeveloping DevTools Concepts Read the complete protocol