HTML Checking for Large Sites
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Duplicate ID “X”.
The id attribute is used to identify a single element within a document, and is required to be unique. Check the document for repeated IDs.
Related W3C validator issues
The id attribute is used to identify a single element within a document, it’s not required, but if used it must be unique, and must not be an empty string.
Element IDs in an HTML document must be unique. The HTML validator is indicating the first occurrence of an ID that is repeated. Check the details for that issue to see web pages affected, and the elements within them, to fix that ID repetition.
In the days before HTML5, named anchors were used as a way to provide a link to a specific section of a document, for example:
<h2>
<a name="section-5">Section 5</a>
</h2>
Now in HTML5, the name attribute is obsolete for <a> tags, and instead, you can use the id attribute of any element (not just <a>) as a way to navigate directly to it, for example:
<h2 id="section-5">Section 5</h2>
Read more about:
<label> tags are used to label inputs in form, which need to be present and visible in the document, for example:
<label for="age">Age</label>
<input id="age" />
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