CSS Explained: Why Is not My :nth-child(1) Selector Working?

Have you ever been confused why `:nth-child(1)` fails to select your intended first element, forcing you to use `:nth-child(2)` instead? This isn't a bug, but a common misunderstanding of how `:nth-child` actually works. This article from wiki.lib00.com delves into the two-step filtering mechanism of `:nth-child`, illustrates its key differences from `:nth-of-type` with clear examples, and helps you permanently solve the 'off-by-one' issue in your CSS selectors.