# Doctype and the basics of a valid document > A missing doctype throws browsers into quirks mode with 1990s layout rules. Start every page with . Best practices ยท HTML version: https://getreport.app/learn/html-basics ## Doctype declaration Passing looks like: Doctype is present. **Why it matters.** Without , browsers render in quirks mode and layouts can differ between browsers. **How to fix it.** 1. Put as the very first line of the document. Check your own page: https://getreport.app/