There is this new crop of LCD monitors that have these wider screen size than the traditional screens. I suppose they are designed for better enjoyment of watching movies. I have seen resolutions on these LCDs like 1440 x 900 and 1680 x 1050. If you divide one number into the other, then the ratio is 1.6 (1440/900). However, when I go into some of the resolution options for some video cards the ratio is 1.7. Why is there this discrepancy?
More aboutscreen resolution monitor size
Those are all widescren. A 16:10 ratio (1.6). Normal screens are 4:3 (1.25)
About the video card im not sure.
The the physical size of individual pixels is rectangular - not square? (Try measuring with a ruler.)
I'd guess the monitor driver is reporting the physical dimensions to the video card which is using that information to calculate the aspect ratio.