HTML Guide for non-empty

Bad value “” for attribute “href” on element “link”: Must be non-empty.

href
link
non-empty

Bad value “” for attribute “src” on element “iframe”: Must be non-empty.

iframe
src
non-empty

An <iframe> element allows to embed an HTML document inside another HTML document, and its src attribute is indicated the source URL of the embedded web page. The src attribute is a required attribute, so it cannot be blank.

Example:

<iframe src="https://example.com/map.html"></iframe>