When this command is used, the player's browser will immediately attempt to leave the story's page, and navigate to the given URL in the same tab. If this succeeds, then the story session will “end”.
If the given URL is invalid, no error will be reported - the browser will simply attempt to open it anyway.
Much like the
<a> HTML element, the URL is treated as a relative URL if it doesn't start
with “http:”, “https:”, or another such protocol. This means that if your story file is
hosted at “http://www.example.org/story.html”, then
(open-url: "page2.html") will actually open
the URL “http://www.example.org/page2.html”.