Hey, I just thought it would be easier to tell it like this...
So I made this, yes, it's very stupid but I was just trying out.

This is how the picture looks when I save it(up)
And this is how it looks like in photoshop (down)
If you look closely you can see that they are different...

Now, do you have any idea why is that happening?
P.S. Can you recommend me some stuff I should do on the picture to make it look better?
Update: Everything is OK. It's just that Windows XP's Picture Viewer isn't good enough so it showed low quality picture.
Sorry for your time.