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Common HTML Validation Errors.

Creating clean and error-free HTML code is essential for building well-structured and functional websites. However, even experienced developers can encounter common HTML validation errors. These errors can impact the way your website displays on different browsers and devices. Fortunately, most HTML validation errors are relatively easy to identify and resolve.

This blog post equips you with the knowledge to tackle these errors head-on, ensuring your HTML code is valid and your website functions flawlessly.

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Common HTML Validation Errors

Missing or Mismatched Tags: Maintaining Balance

One of the most frequent HTML validation errors involves missing or mismatched tags. HTML relies on opening and closing tags to define the structure of your webpage content. A missing or mismatched tag disrupts this structure and can lead to unexpected display issues.

Missing Closing Tags

Sometimes, developers forget to include the closing tag for an element. For instance, forgetting the closing </p> tag for a paragraph element can cause the browser to continue interpreting subsequent content as part of the paragraph, leading to formatting problems.

Mismatched Tags

Another common error involves using the wrong closing tag for an opening tag. For example, accidentally using </h2> to close a <h1> element can disrupt the heading hierarchy on your webpage.

Resolving the Errors

Fortunately, resolving these errors is straightforward. Utilize a code validator or a code editor with syntax highlighting to pinpoint missing or mismatched tags. Once identified, simply add the missing closing tag or correct the mismatch to ensure proper element structure.

Incorrect Attribute Usage: Understanding Syntax

Another category of common HTML validation errors stems from incorrect attribute usage. HTML elements often utilize attributes to provide additional information or functionality. Using attributes incorrectly can lead to validation errors or unexpected behavior on your webpage.

Missing Required Attributes

Certain HTML elements require specific attributes to function properly. For instance, the <img> element requires an src attribute to specify the image source. Omitting this attribute will result in a validation error.

Incorrect Attribute Values

Attributes can have specific value formats. For example, the href attribute in an <a> element (used for creating links) must contain a valid URL. Using an incorrect format for the attribute value will trigger a validation error.

Resolving the Errors

To address these errors, ensure you understand the required attributes for each element you’re using and provide valid values according to the expected format. Refer to HTML documentation or online resources for detailed information on specific element attributes.

 Maintaining Structure

Common HTML validation errors can also arise from unclosed elements and content model violations. HTML elements have a defined structure, specifying the type of content they can contain. Violating these content models can lead to validation errors.

Unclosed Elements

Similar to missing closing tags, some elements, like <br> (for line breaks) or <hr> (for horizontal lines), are self-closing and don’t require a separate closing tag. However, accidentally including a closing tag for these elements can trigger a validation error.

Content Model Violations

Each HTML element has a defined content model, specifying the type of content it can contain. For instance, an <h1> element can only contain text content, not other HTML elements. Inserting an <img> element within an <h1> element would violate the content model and result in a validation error.

Resolving the Errors

For unclosed elements, simply remove the unnecessary closing tag. To address content model violations, ensure the content you place within an element adheres to its defined structure. Refer to HTML documentation for detailed information on content models for various elements.


By understanding and resolving common HTML validation errors, you can create clean, well-structured, and error-free code. Valid HTML code ensures consistent rendering across different browsers and devices, ultimately enhancing the user experience of your website. Furthermore, adopting good coding practices from the start helps prevent these errors in the future, saving you time and frustration in the long run. So, embrace valid code, conquer validation errors, and watch your websites flourish!

By Daniel