# Web essentials > The document fundamentals The document-head fundamentals every page needs — viewport, charset, language, favicon. AI scaffolds routinely skip them because the generated component owns the body and nobody edits the base HTML document. Caught by the web-essentials detector — 4 document-head checks. ## Problems in this category - [Missing viewport meta tag](https://vibecheck.wcgw.fun/fix/missing-viewport-meta.md): Without a viewport meta tag, mobile browsers render your page at desktop width. Add one line to make the layout responsive again. - [Missing charset declaration](https://vibecheck.wcgw.fun/fix/missing-charset.md): A missing lets browsers guess your encoding, mangling emoji and accented text. Declare UTF-8 as the first tag in . - [Missing lang attribute on ](https://vibecheck.wcgw.fun/fix/missing-lang-attribute.md): A missing lang attribute stops screen readers picking the right voice and search engines detecting language. Add lang to your element. - [Missing favicon](https://vibecheck.wcgw.fun/fix/missing-favicon.md): No favicon means a blank browser tab and a 404 on every load. Add a so your site is recognisable in tabs and bookmarks. --- Category index from VibeCheck — https://vibecheck.wcgw.fun/fix/essentials. Full site index for LLMs: https://vibecheck.wcgw.fun/llms.txt