What produces a warning

Content the extension can’t render faithfully produces a warning naming the declaration, instead of disappearing from the page. These aren’t live examples: this site builds with -W, so a real warning would fail it.

In your source or page	What the warning says	Category
/// Markdown comments	Markdown documentation comments are not supported	java.extract
An unknown block tag, such as @todo	Unsupported block tag UNKNOWN_BLOCK_TAG	java.extract
External snippets, regions or markup	Unsupported snippet attributes or markup	java.extract
{@link} to a symbol the compiler can’t find	Unresolved Javadoc reference	java.extract
{@inheritDoc} without ancestor source	Cannot resolve inheritDoc	java.extract
An HTML element outside the supported subset, such as <h3>	Unsupported Javadoc HTML <h3>	java.html
A :members: entry that doesn’t exist	Java member … was not found	java.member
The same declaration documented twice without :no-index:	Duplicate Java documentation	java.duplicate
An overloaded method named without parameters	Ambiguous Java reference	java.ambiguous

Unsupported content stays in the page as literal text where possible, such as [unresolved inheritDoc]. See Troubleshoot a documentation build for fixes and Supported Javadoc for the supported content.