For posting images on FAA, I do 100% quality, 300ppi, sRGB and leave the file the size it was originally (up to 25MB). Also use FAA's watermark.
Now to upload images to my personal sites is a way different story: 60-70% quality, 600px long side, 72ppi, sRGB and file size no more than 60kB (that's right kilobytes). No watermark
~ Charly