I am seeing the following "oddity" with IE7-10 on Windows Vista, 7, 8:
When declaring font-family: serif; I am seeing an old bitmapped serif font that I can't identify (see screenshot below) instead of the expected font Times New Roman. I know it's an old bitmapped font because it displays aliased, without any font smoothing, with IE7-10 on Win Vista-8 (just like Courier on every version of Win).
Screenshot:

I would like to know (1) can anyone else confirm my research and (2) BONUS: which font is IE displaying?
Notes: IE6 and IE7 on Win XP displays Times New Roman, as they should. It doesn't matter if font-family: serif; is declared in an external stylesheet or inline on the element. Quoting the CSS attribute makes no difference. Adding "Unkown Font" to the stack also makes no difference.
New Screenshot: The answer from Jukka below is correct. Here is a new screenshot with Batang (not BatangChe) to illustrate. Hope this helps someone.

serifas a fallback without Times New Roman or Georgia is not a good idea. Thanks for the help. – Jeff Sep 11 '12 at 13:04<html lang="en">or in phpheader('Content-language: en');) – Olly Hodgson Sep 12 '12 at 15:31langattributes, and also without any, with the same result (Batang). – Jukka K. Korpela Sep 12 '12 at 15:54<html lang="en">. – Jeff Sep 12 '12 at 21:41