Currently, whenever I open a new page containing any Stack Overflow content: main page, tagged questions, an individual question, user profile, anything, all content is completely unstyled, as if all CSS was removed. I did View Source, and this style sheet reference is present.
<link rel="stylesheet" type="text/css" href="http://sstatic-a.akamaihd.net/stackoverflow/all.css?v=fca729ed9ab4">
Navigating to that site, I can see that my company blocks content from that site.
Meta Stack Overflow is not affected; the CSS link here in Meta appears to be locally hosted.
<link rel="stylesheet" type="text/css" href="/content/stackoverflowmeta/all.css?v=36683b668064">
I've seen this behavior before on Stack Overflow. Is this another test? How often are these tests? Will the tests stop at some point?
EDIT
All CSS content appears to have been restored on Stack Overflow. The CSS link has changed to
<link rel="stylesheet" type="text/css" href="http://turbo-test.cdn.sstatic.net/stackoverflow/all.css?v=fca729ed9ab4">