Point to a page with a long description of the content of the <iframe>:
The <iframe> longdesc attribute is not supported in HTML5.
The longdesc attribute specifies a URL to a page that contains a long description of the content of an <iframe>.
Note: The longdesc attribute is so poorly supported that it should not be used. To offer a long description of an <iframe> (if necessary), simply create a link (that is visible to anyone) to a page with the description.
|longdesc||Not supported||Not supported||Not supported||Not supported||Not supported|
|URL||A URL to a page that describes the content of an <iframe>.