The first test.

Here the longdesce attribute points to the iframe element while the iframe points to the long description.

The second test.

Here both the longdesce attribute and the iframe element points to the long description.

Test for browser users without contextual menu for longdesc

Clicking these links should give you the same experience as when opening a longdesc link via a contextual menul:

• Test what happens when opening the first longdesc link: First longdesc..
• Test what happens when opening the second longdesc link: Second longdesc..

Note about this page

Both images are the same. Thus the longdesc should also be the same. But in the first case, the longdesc points to a hidden iframe. This iframe become visble via the :target{} CSS selector. And, typicall, when a long description is read, it is read in a new browsing context which thus gives focus to that iframe — so that it becomes visible.

The second test uses a normal longdesc.