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Table of Contents
1. Missing required attributes
2. Improperly nested tags
3. Invalid or deprecated tags
4. Character encoding issues
Home Web Front-end HTML Tutorial Debugging common HTML validation errors.

Debugging common HTML validation errors.

Jul 03, 2025 am 02:41 AM
HTML Verification

<p>When encountering HTML verification errors, you must first clarify the problem and correct it according to the specifications. 1. When the required attributes are missing, the src and alt and a href of img should be completed; 2. When the tag is nested incorrectly, the structure should be clarified and the tags should be closed correctly to avoid confusion in nesting block-level elements; 3. When using invalid or discarded tags, you should refer to the MDN document to replace it with modern writing methods, such as replacing center and font with CSS; 4. When character encoding problems, add meta charset="UTF-8" and ensure that the file is saved in UTF-8 format to solve it.

<p>Debugging common HTML validation errors.

<p> Don't panic when encountering HTML verification errors. Most problems are actually quite common and easy to solve. The key is to understand the meaning of the error message and know how to change it. Below we have compiled several of the most likely HTML verification errors to encounter and the corresponding processing methods.

Debugging common HTML validation errors.

1. Missing required attributes

<p> Some tags require specific attributes to pass verification, such as <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175148166575363.jpeg" class="lazy" alt="Debugging common HTML validation errors." > must have src and alt , and <a></a> must have href . If you miss these properties, the validator will report an error.

Debugging common HTML validation errors.<p> How to deal with it:

  • See the specifications and requirements of each label clearly
  • Pay special attention to form elements and multimedia related tags, which usually require strict attributes.
  • For example, the <input> tag should contain at least type and name
<p> For example:

Debugging common HTML validation errors.
 <!-- Error writing-->
<img  src="/static/imghw/default1.png"  data-src="photo.jpg"  class="lazy"  alt="Debugging common HTML validation errors." >

<!-- Correct writing method-->
<img src="/static/imghw/default1.png"  data-src="photo.jpg"  class="lazy" alt="Description Picture Content">

2. Improperly nested tags

<p> Label nesting errors are common problems for beginners, such as applying <div> in <p> , or opening a new label if you forget to close a tag.

<p> Why errors occur:

  • HTML structure is not clear, especially when multi-layer nesting is more likely to get confused
  • If the editor does not have automatic completion or indent reminder, it is easy to ignore it
<p> Solve Suggestions:

  • Close it immediately after writing a tag and add content to it
  • Use the automatic formatting feature of the code editor to check the structure
  • Common error combinations such as <p><div>...

are not allowed because <div> is a block-level element and cannot be placed in <p>

3. Invalid or deprecated tags

<p> Sometimes we accidentally use labels that have been eliminated, such as <center> , <font> , or some old labels that are not supported by HTML5.

<p> How to determine if the tag is invalid:

  • Check the specific prompts given by the validator, and usually say "Element is obsolete"
  • Refer to the official MDN document to confirm the tag status
  • Rewrite with modern alternatives, such as controlling styles with CSS instead of relying on old tags
<p> for example:

 <!-- Obsolete writing-->
<center>Chinese characters</center>

<!-- Recommended writing method-->
<div style="text-align: center;">Chinese characters</div>

4. Character encoding issues

<p> The page appears garbled, or the validator prompts "character encoding" error, usually the correct character set is not set.

<p> The solution is simple:

  • Add this line to <head> :
     <meta charset="UTF-8">
  • Make sure your file is saved as UTF-8 encoding (most editors can set)
  • This is especially important if you use Chinese or other non-English characters
  • <p> Basically that's it. Although HTML verification errors may seem annoying, they are mostly small structural or syntax problems that can be quickly fixed as long as you pay attention.

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