I honestly don't know. Wikipedia's information on this HTTP status code is obscure:
Wikipedia wrote:406 Not Acceptable
The requested resource is capable of generating only content not acceptable according to the Accept headers sent in the request.
However, the Wikipedia page on Content Negotiation says:
Wikipedia wrote:Content negotiation refers to mechanisms defined as a part of HTTP that make it possible to serve different versions of a document (or more generally, representations of a resource) at the same URI, so that user agents can specify which version fits their capabilities the best. One classical use of this mechanism is to serve an image in GIF or PNG format, so that a browser that cannot display PNG images (e.g. MS Internet Explorer 4) will be served the GIF version.
A resource may be available in several different representations; for example, it might be available in different languages or different media types. One way of selecting the most appropriate choice is to give the user an index page and let them select the most appropriate choice; however it is often possible to automate the choice based on some selection criteria.
So, I'd most likely choose the second option -- that they're doing maintenance on their site, and the resources your accessing has a UA it doesn't recognize. I just went to the log in page though and it works perfectly fine for me... not sure if its your browser or what.
"On two occasions I have been asked [by members of Parliament!]: 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out ?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question." — Charles Babbage.
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