My guess is that your editing software does a much better job simplifying the image for display on your lower resolution (than image) monitor. Web browsers do not do this very elegantly. Sharpening your image will exasperate this. My suggestions are to:

(1) Always review your image with your browser before you upload.

(2) If the image looks lousy in your browser, then resize appropriately (800x600??), resharpen, and then post. I typically have two files for each finished image: "hi-res" for prints and "small" for the net.

BR,
Tim