Secretary of Homeland Security Janet Napolitano unveiled revamped and simplified terror alert procedures Wednesday that replace the multicolored terror alert chart with only two levels -- elevated and imminent – and without the colors.

Speaking in New York City's Grand Central Terminal on a balcony overlooking the major mass transit hub, Napolitano said the new system is designed to make Americans more alert and provide more specific and credible warnings about possible terrorist threats.

"It will provide alerts based on specific, credible information about potential terrorist activity. The alerts will give you as many details as we can provide in an unclassified form. They will say how you can help, what you need to do to stay prepared."

The new terror alert site is www.dhs.gov/alert. The department will also send alerts by Twitter and Facebook.

In a small meeting with several members of the media prior to her announcement, Napolitano quipped that "the colors were out there, but there was no information backing them up. Nobody paid attention to them other than David Letterman and Jay Leno. We think this will be much more helpful."

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The old warnings included the colors of green, blue, yellow, orange and red, indicating levels ranging from low to severe. That was too vague, Napolitano said, noting that the terror level at airports has remained at "orange" since 2006.

The new system will be specific to locations, types of potential attacks, even indicating what authorities would be looking for, either as a suspect or specific type of attack, such as a bomb.

Napolitano said the normal status for the country is "high risk," and that the new system should clarify the types of threats.

"Elevated is above normal base line. Imminent is very time sensitive, and we are trying to get people to react in a very time sensitive manner."

Napolitano said that the goal of the new system is to also "to advise people what to look for and what and how to protect, prepare, protect themselves and their families" in a manner that is more detailed than the color system.

She also unveiled the public service advertisements for a new effort for shared responsibility, the "See Something, Say Something" campaign that is "designed to have people be more active and just know that they have a role to play."

Napolitano has noted that the campaign will focus on airports, transportation centers, stadiums and other possible areas that experts have considered potential targets.

Asked her about efforts to thwart radical Islamic extremists inside the U.S., Napolitano cited "neighborhood community policing, where the police are really trained on what to recognize and how to build bridges with particular communities, just as we did in fighting some of the gang wars in the '80s and early '90s." That strategy now is being employed to combat "trans-behaviors that are indicative of violent extremism that is moving from ideology to actual commission of acts of violence."

Former federal terrorism prosecutor Andrew McCarthy said that addressing the underlying causes will be a key to protecting our country.

"I never thought that color coding made America safer to begin with," McCarthy told Fox News. In the 1990s, McCarthy prosecuted the blind Sheikh Omar Abdel Rahman Rahman for the 1993 World Trade Center bombing and El Sayyid Nosair, a mantenance man in Rahman's terrorist cell, for the assassination of a rabbi.

"If you want to stop terrorism, you need to be able to predict what the terrorists will do next. You can't do that without understanding how they act in the first place, and because Islamic terror has a profound connection to Islamic ideology and Islamic doctrine, we haven't wanted to grapple with that, and I think until we do, we can't make ourselves as safe as we ought to be."

McCarthy added: "You could do everything right, and they only need to get lucky once. They are here and they are trying. I mean, we need to recognize that these guys hate us, and if they could attack us and had the opportunity to do it, they would."

Republican New York Rep. Peter King called Homeland Security's new alert system the "right step."

"I think the color-coded system did work better then people gave it credit for, but it is time to move on," King, chairman of the House Homeland Security Committee, told Fox News.

The new, improved system will be "much more threat-addressed," he said. "It's only going to raise the level when there's been a significant change and it will also notify the specific industry area that is being threatened."

A recent study by the Institute for Homeland Security Solutions, an independent think tank, found that between 1999 and 2009, there were "86 foiled and executed terrorist plots against U.S. targets." Secretary Napolitano has noted that 80 percent of them were stopped by observations from law enforcement or citizens who spoke up.

"We don't want people to live in fear," she noted. "We want people live in a state of alertness and awareness."