Why Computers should work only on 0 and 1 ?

Everybody knows that Computers work only on 0 and 1.

Nowadays its positive and negative.
Its because its a base two system (binary), so only the first two numbers are used, 0 and 1. Binary was written about and used long before we had circuitry, IIRC Leibnitz was the first to write about it in terms of 0s and 1s back in the 1600s. Though ultimatly it would be boolian algrebra that proved the worth of a binary system in electrical switching circuits. At least, IIRC.

I think computers dont have any idea about maybe?So It is yes or no?

Quantum computers do ;)

People had been playing with the notion of binary for, well since ancient times i beleive (various divination systems used it, hell still use it i guess), though its so contrary to the natural human way of thinking (try converting 64 bit addressing from binary to denary and back again, in your head, with no pen and paper, it takes ages and its no fun, and i thought 32 bit was bad), that not alot came of it on the mathmatical application front.

Leibnitz wrote of the notion sometime in the 1600s ( a treatese of sorts IIRC) and specificly used a '1' and a '0' and thus is often credited with the modern invention of the binary system used in computers, though really that has more to do with boolian algebra which actualy made use of a binary system in a way that computers would later use.
I don't know alot about Leibnitz (other than that he also discovered some calculus stuff indipendantly of Newton), i just know the above from my limited knowledge of computing.

Quantum is, well quantum, and tends to hurt your brain when you dwell on it to much. But the essence of quantum computing is that, as well as a '0' and a '1', you can have a '1 and 0', a '1 or 0', or even 'somewhere between 1 and 0'.
Basicly i think it allows an individual bit (or qubit as its called - quantum bit) to be a complex number as opposed to a mere real number. Or something.

In theory a serious quantum computer will be able to make computations of a much higher order and at much greater speeds than the 'classical' computers we use today, though it will be a few years yet before most of us ever get to even see one, let alone use one (though thats unlikely either, they are more for serious number crunching, than brwosing the internet or whatever).