How to Fix the 10 Most Common HTML Errors

Every HTML validator report has the same usual suspects. Here are the 10 errors I see most often,with the fix for each one. I built ValidateHTML to catch these automatically, but knowing why they matter is just as important as fixing them. 1. Missing alt Attribute on Images Every <img> needs an alt. Screen readers depend on it. Google Images indexes it. It's the #1 accessibility violation on the web. ❌ Invalid: <img src="hero.jpg"> ✓ Valid: <img src="hero.jpg" alt="Mountain landscape at sunset"> For decorative images, use alt="". 2. Unclosed Tags A missing </p> or </div> can shift your entire layout. Browsers auto-close silently,usually wrong. ❌ Invalid: <div class="card"> <p>Some content </div> ✓ Valid: <div class="card"> <p>Some content</p> </div> 3. Deprecated Elements <center>, <font>, <marquee>,still render, but signal outdated code. ❌ Deprecated: <center> <font size="5" color="red"&