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HTML Guide

Bad value “X” for attribute “for” on element “label”: An ID must not contain whitespace.

The <label> element represents a caption in a document, and it can be associated with a form input using the for attribute, which must be an ID. Document IDs cannot contain whitespace.


  <label for="user_name">Name</label>
  <input type="text" id="user_name" />

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Related W3C validator issues