other point its the format a jpg format its very complex when you download images its for sure that they work with more than 80 % of quality image ....when your reduce this percent value you loose definition in your work other think its that your original work always must be big like 1600 x 1200 pixels at 72 dpi minumun then you can reduce the work you want to post in the galery, and check that your work in rgb and with adobe (psd) format...if you somtime need print your work well now you need 300 dpi per inch minimun the best its 350 dpi per inch but 20 megas letter images, good luck