Preparing images for the web
As mentioned before, and to reiterate, here is the workflow i would start with:
Load original image.
Make flattened duplicate.
Close original image.
If color space other than sRGB, CONVERT to sRGB.
Resample image to exact pixel proportions as shown on the web site. This step is very important. If images reproduced on the web page are NOT 1:1 in pixels, then the browser is forced to do interpolation, either up or down, and thus WILL introduce artifacts, such as pixellation in the case of undersized images, or wavy and wonky lines in the case of oversized images.
Do USM 500, 0.2, 0 to clean up resampling softness.
File > Save for Web (will strip EXIF data), medium or high quality.
Close the duplicate image without saving.