“Is rendered item valid XHTML document” validation error in Sitecore can occur due to multiple reasons but most common is while Approving an item (in Review tab) due to HTML5 tags in Rich Text field default Sitecore item.

The Validation Rules are configured –

/sitecore/system/Settings/Validation Rules/Global Rules

So when we try to Approve an item, Validation rules are run by sitecore.

Solution:

• Remove “Full Page XHtml” from all Validation rules of  /sitecore/system/Settings/Validation Rules/Global Rules .

• Remove “Full Page XHtml” from all Validation rules of /sitecore/system/Settings/Validation Rules/Field Types/Rich Text .

This will disable the XHTML validation and resolve the error.

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