"Oh, no you di'int!"

Solution 1:

The phrase "oh no you di'in't" is frequently used in response to an action that is contrary to the commonly accepted custom or etiquette, but of which the speaker nonetheless approves, either because the situation has been made humorous by the unexpectedness and incongruity of the action, or because the action is seen as serving some greater good despite its perceived impropriety.

Solution 2:

Oh no [he/she/you/etc.] didn't! is a clichéd phrase for expressing disapproval or incredulity at some event or utterance, though the degree of either is variable. Dpending on the delivery and context, it might indicate anything from a mildly humorous observation to genuinely shocked outrage. The corresponding return is Oh yes she did!, also to be delivered theatrically, perhaps with a finger wag, head bob, finger snap (0:22), or other gestures that have been associated with, to use TVTropes' name, the “Sassy Black Woman” character.

It probably cannot be traced to a single point of origin. Surely schoolchildren have debated the question of whether something was or was not done by someone employing this phrasing for some decades. The phenomenon of its affected pronunciation was discussed on LinguistList as far back as November 2004 in the thread "di?nt" (with glottal stop), where it is observed in Northeastern (US) and in African-American Vernacular English, but is not limited to either. Note also that the question of whether di'nt reflects a glottal stop (as in some British accents) or deletion is brought up but not resolved.

As Ben Zimmer writes:

In recent years the exaggeratedly glottalized "Oh no you/he/she di[?]n't" (as a response of outrage, or mock outrage) has become a hackneyed catchphrase. My sense is that the expression had its origin in hiphop and then started turning up on those "trash TV" shows in the late '90s (with appropriate hand gestures and head-bobbing). From there it became a source of mockery for white Americans, as in this bit from Saturday Night Live's "Weekend Update" (April 2002):

http://snltranscripts.jt.org/01/01pupdate.phtml

Tina Fey: (nods head) Bill Clinton - Bill Clinton revealed in Newsweek that he is getting a new chocolate lab to replace his dog, Buddy. Bill says, with Hillary away in D.C., he just needs another bitch in the house.

Jimmy Fallon: Oh, snap! Oh, yes, you did!

Tina Fey: (gets up from her chair and starts flapping arms) Oh, no! Oh, no, you didn't! Oh, snap! OKAYYYYY! [etc.]

He finds examples from Usenet dating back to the mid-1990s, for instance

Date: 1994/04/20
Message-ID: <94110.191901SCW112 at psuvm.psu.edu>
Newsgroup: alt.rap

In article <1994Apr20.214045.27522 at random.ccs.northeastern.edu>, nickman at ccs.neu.edu (Jeff Nicolai) says:

- Chuck D. from Public Enemy is from a middle class family in Long Island. As an 'oppressed' rapper from the ghetto........ he ain't Shit!!!!

oh no you didn't...

and

Date: 1995/08/03 Message-ID: <030895.10035334596.n at frontier.canrem.com> Newsgroup: rec.music.hip-hop

Da Brat and Latifah are lesbians. Please don't deny it...

UH, oh no you DIDN'T! Latifah I ain't care aboutm but, but tha Brat? That's cold man, that's cold.

If its wider acceptance in the culture also stems from that period, it may be attributable to the popularity of television shows like Martin or In Living Color, where some characters used exaggerated inner-city speech.

Solution 3:

It means - Oh no ! You didn't say THAT ! How awful !

In response to something awful said to you, like an insult, or just

something completely outrageous, like "I swore at the boss !"

From Urban Dictionary:

oh no you di'int A response to a bold statement, accusation, or action; slang for "you're going to wish you hadn't said/done that," or "bitch you'll pay for that." "Yo momma's so fat, I poked her in the belly and gravy came out."

"Oh no you DI'INT!"

http://www.urbandictionary.com/define.php?term=oh+no+you+di%27int