what is the significance of red alert.?

Answer 1

It means there has been a major attack.

Answer 2

Red was the British Civil Defence action warning 'Raiders Approach', receipt of which would authorise the sounding of the audible sirens on a two minute fluctuating or warbling note of varying pitch giving 12 minutes advance warning of the enemy's arrival.
www.fishponds.freeuk.com/nluftbri4.htm

the highest level of alert when an attack by the enemy seems imminent (or more generally a state of alert resulting from imminent danger)
wordnet.princeton.edu/perl/webwn

Red Alert is a 1958 novel by Peter George about nuclear war. The book was the basis for Stanley Kubrick's film, ''''. It differs significantly from Kubrick's movie in that it is not a comedy.
en.wikipedia.org/wiki/Red_Alert_(book)

Red Alert is the highest state of alert for Starfleet in the Star Trek fictional universe. Red alert may be called on starships, installations, regions, or the entire fleet.Aboard Starships, it is similar to a call to "General Quarters" aboard real-life Navy vessels.
en.wikipedia.org/wiki/Red_Alert_(Star_Trek)

Command & Conquer: Red Alert, is a real-time strategy computer game in the Command & Conquer series by Westwood Studios. The game is an alternative history where allied forces defend Europe against an aggressive Soviet Union. It was available for PC (DOS & Windows 95 versions included in one package) and was subsequently ported to PlayStation.
en.wikipedia.org/wiki/Red_Alert_(computer_game)

Answer 3

To inform us that they are STILL looking for Bin Laden. So of course, since he is still out there than anything can happen.

Whatever.

Answer 4

It means there is a seriouse threat to our country

Answer 5

http://www.oilempire.us/redalert.html