If this is the case, I think the article could have made it more clear that the problem was with software not under the author's control. All the article mentions is "the application registering the device," and I assumed that it was their application which was not sending the header. So a browser won't send a Content-Length header for a PUT request if there is no body?

I'm not criticizing the article itself; it was a nice beginner guide to making quick changes to an existing C project. My only criticism is that the first step when considering whether to make a change to a code base is to fully evaluate whether that change is appropriate, if it is fixing the problem in the right place. Perhaps the author did this and the article simply failed to mention it.

do browser support put at all?

The good news is that browsers aren't the issue for us at Urban Airship. The bad news is that it's worse: it's an infinite number of HTTP libraries of varying quality that hit our API. Some from pretty much every imaginable platform capable of HTTP: from mobile devices to VBA in Microsoft Access:

http://help.urbanairship.com/discussions/questions/161-using...

If the HTTP standard allows it, we probably need to support it (or degrade in a standards compliant way) because someone will try to use it.