Floating point accuracy

I have written a shader to show a slice of a 3dimensional volume texture.
the data loaded was .raw file. the values in the file were USHORT values.
When the outputted data was analyzed there was a mismatch between the actual value inputted and the resultant value. When I searched the net I came across an article saying that in NV40 cards odd floating point numbers cannot be shown accurately if the number is above 2048. But I am using G70 graphics card(7800 GTX). Does this card also have the same problem. Any Guyz facing the same problem

Where have you read it? G70 architecture is derived from NV40, maybe they brought behind something...

I have read it from a site called "http://www.3dcenter.org/artikel/nv40_technik/index3_e.php" . In that site it was given that NV40 series has such a problem.

Well, floating point values cannot be represented exactly by computer hardware, it is always approximation to some degree. As for GPU, shader model 3.0 defines partial (FP16 - 16bit per component) and full (FP32 - 32 bit per component) precisions in which numbers can be stored.
Can you show your shader code and the numbers you're using/getting? If you're using some large numbers, some precision is always lost, as more bits are needed to store the part before decimal point.