http://www.botany.hawaii.edu/faculty/webb/Bot410/PicassaTutorial/PicasaImageSize/PicasaImageSizing-1.htm

Now a variation on this is use the jpg quality.. slide it down. It will leave the image the same size but will reduce the quality. Since anything over 72dpi is wasted for on screen viewing, reduced quality is not a problem. Just make sure to save your original image first.

I would reduce the quality of the image and the size. You don't need to post anything bigger than 640x480 for nice viewing online.