Google Chrome spell check confusion

I just saw something unusual behavior in Google Chrome's inbuilt spell check feature. This feature highlights wrong spellings with a red underline while typing in a textbox. But my do开发者_Python百科ubt is, how can it under-line a the same word when all letters in the word are in small case, eg - facebook

and again when i type the same word with the first alphabet in Uppercase, eg - Facebook, the word is not underlined.

Here is the snapshot:

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Facebook only refers to one thing-the name of one particular website. That makes it a proper noun, and so it should be capitalized. That's in the same vein that "person" or "website" (generic common nouns) are not capitalized, but "Jim" and "Facebook" (referring to a specific person or website) are.

While writing this post, incidentally, I've found that Firefox has the same behavior-write firefox or facebook and you'll get the red line, but Firefox and Facebook are not flagged.

So, basically, Chrome is correctly flagging a misspelling, or at least a capitalization error. Facebook is correct, facebook is not.