The Element tab
What the side panel shows for the selected element, and where its CSS sits.
Select an element and open the side panel. The Element tab shows its selector, size and box model, then the CSS behind it. The Code section opens on Computed, and its menu switches between Computed, Rules and Changes. Warnings, shadows and gradients sit above Code, and Stacking below it; they appear when they apply. See Warnings, effects and stacking.
Questions
What does the Code section open on?
Computed. Its menu switches between Computed, Rules and Changes.
Why do some sections only sometimes appear?
Warnings, shadows and gradients, and Stacking appear only when they apply to the selected element.