RFC 2616: For 5xx error codes, <i>User agents SHOULD display any included entity to the user.</i> If your server serves up HTML on a 500, it should get rendered. This page happens to serve up HTML.<p>Why? Well, the server administrators would have a better idea after investigating than I do.<p>If I were playing the percentages, I'd guess "a poorly coded WordPress plugin is causing rendering the index page to time out <i>after</i> all content has been sent down the pipe; Apache then terminates the connection with a 500 error and sends down all the content it buffered locally prior to the timeout, which in this case happens to be everything."<p>Circumstantial evidence: no errors on rendering static resources even though they appear to go through the same server. Other dynamic pages show very long time to first byte but sporadically give HTTP 200s; I'm assuming that they render completely and return control before Apache times out the PHP.