maintenance mode registers as 503?

The page itself is viewable, but it seems odd that Firebug would call it a 503. Perhaps this is as design?

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Quote from veneanar

It works as intended. Important for crawler/bots. So they know that they have to abort indexing and revisit in near future. See http://en.wikipedia.org/wiki/List_of_H…xx_Server_Error

Thank you for explaining that. That makes sense. Thanks @veneanar