I try to make all my works as high resolution, so I can prepare for print in the future. so I work in photoshop and set the color for prepress use.but I also like to make each images as a small jpeg version. so I can post on the web.However the jpeg image color fade out a lot when i converted it from photoshop.and that is not color I want. any way I can work on both prepress and web and set the color close enough ? I never realize this before.and whatever i changed the image format, the color look the same. now I just do my color calibration on my monitor, should I calibrating for prepress? or for web? the color look SO different.

calibrate for whatever is most important to ya. On the web, everyone has a different calibration setting anyways, so while it'll look perfect on yer screen, it'll look like shit on someone elses. worst case scenario, when you make a small jpeg version, adjust the colours manually.

the easiest way is to build in CMYK then convert to RGB. since the RGB gamut is way larger than the CMYK gamut, your not going to include colours that can't be printed. Use Adobe gamma to calabrate your monitor, go to you color prefs and select that as the RGB work space. here is a sample of my settings