How the New Yorker renders articles after quota

When you've read your 4 articles for the month at thenewyorker.com, it renders the first few lines of the article then a message that you need to subscribe to read more. However it has given you the whole article, just not in HTML. The HTML tags are rendered thusly:

Quote:

["p",

for <p>
The closing tags are: Quote:

],

, relying on nesting to know what they close.

Is this a general convention, or one thenewyorker has invented? I just clear my cookies and try again.