Save For Web problem

In pscs2 (photshop cs2) whenever i try to save an image for web its darker then wht i made it , any reson on how to correct this problem

test with PNG file type, to make sure it's not just the low quality of gif/jpeg/whatever you're using that's causing the darkness.

naw i tried all the qualitys, i think i found the soulution its the colour settings, scince i bought a new 21"samsung monitor i had to calibrate the settings