Despite warnings posted on Youtube by Ayman al-Zawahiri and al Qaeda of attacks set for September 11, the White House and State Department failed to provide adequate security in Benghazi, Libya and other diplomatic posts, contributing to the death of Ambassador Stevens and the other U.S. Personnel there...

Bloody handprint at U.S. Consulate in Benghazi

U.S. diplomatic posts were being targeted repeatedly in run up before the September 11 deadly attacks in Libya.  Despite that, the consulate offices in Benghazi had no Marines and were not fortified.   The decision not to do that rests with Hillary Clinton and the State Department. 

The UK Independent reports:

American officials believe the attack was planned, but Chris Stevens had been back in the country only a short while and the details of his visit to Benghazi, where he and his staff died, were meant to be confidential.
The US administration is now facing a crisis in Libya. Sensitive documents have gone missing from the consulate in Benghazi and the supposedly secret location of the "safe house" in the city, where the staff had retreated, came under sustained mortar attack. Other such refuges across the country are no longer deemed "safe".

Did the White House and State Department have warnings
48 hours prior to the September 11, 2012 attacks?

The White House is denying it had any prior notice.  Jay Carney went so far as to note there was no evidence of pre-planning yet as noted at Ace of Spades that is undercut by other U.S. officials:  

Press Secretary Jay Carney says the White House has no information to suggest that any of the unrest in the Middle East 'was pre-planned.'contrast to...
The attack, which U.S. officials believe could have been planned in advance...

Given the weapons and fighters at the Benghazi attack and from other intelligence, it is believe al Qaeda planned these attacks in advance.   And there were warnings 48 hours in advance from al Qaeda from Ayman al-Zawahiri (ironically posted on Youtube also) urging Libyans to attack to avenge the death of Libyan al Qaeda terrorist.

[A] closer examination of the evidence indicates al-Qaeda orchestrated these attacks, and the movie was just a bogus excuse used to trigger the widespread violence. Even worse, it seems al-Qaeda telegraphed these attacks, and the Obama administration still got caught flat-footed, unaware of the terror group's strength in the region, missing key signals and clues that were out in the open. 

One day before September 11, al-Qaeda chief Ayman al-Zawahri posted a 42-minute video on Jihadist forums urging Libyans to attack Americans to avenge the death of Abu Yahya al-Libi, the terror organization’s second-in-command, whom U.S. drones killed in June of 2012 in Pakistan.In the video, al-Zawahri said al-Libi’s “blood is calling, urging and inciting you to fight and kill the Crusaders,” leading up to a date heralded and celebrated by radical Islamists. 

Another version of the video was actually posted on YouTube on September 9 and yet, President Barack Obama, who has not attended an intelligence briefing since September 5, and his administration did not beef up security at the embassy and consulate on September 11. There were no Marines present to protect Americans abroad, as the Islamic mobs overwhelmed what little security presence there was. 

Update:
CNN is reporting Libyans warned US of attack three days in advance...

Prior EBL Posts:

• U.S. commanded MFO base attacked in North Sinai, casualties reported.
• Barack Obama tweets about campaign shirts as the bodies of slain American personnel are unloaded in the United States.  
• Did Ayman al-Zawahiri and al Qaeda direct the Libya attack that killed Ambassador Stevens.

• Did the U.S. government get 48 hours notice and fail to warn U.S. personnel?  
• President Barack Obama flip flops on whether Egypt is an ally or not.
• How would have H.L. Mencken responded to the media's covering of Barack Obama? 
• Hypocrisy:  Candidate Barack Obama criticized both President Bush and John McCain over deaths...
• Mob chanted "Obama, Obama, there are still a billion Osamas..."
• Mitt Romney:  We should not apologize for American values...
• Sarah Palin:  President Obama apparently cannot see Egypt and Libya from his house...
• It's a Beautiful World We Live In...
• Separated at Birth:  The U.S. Embassy in Cairo and...?
• Embassies attacked, Ambassador to Libya killed, White House apologizes to attackers...
• The Heroes of 9/11:  The Manhattan Boat Lift
• Never Forget:  September 11, 2001