To resize a file in photoshop:Go to IMAGE >image size, that will open an options box, you'll want to make your picture 72 dpi and then type in the width 420 pixels or 360 pixels, I wouldn't go any larger than 420. Also to get the best possible quaility with the compression the resampled image should be Bicubic Sharper. Then save your file again with the save as> under FILE, give it a new name and make sure it is a jpeg then when the jpeg options window opens set the quality no higher than 8. Easy as pie lol!! Here's some screen shots.