Images on websites should be as close to quality as possible yet small for fast loading.
choosing the right format is very important,
jpeg: complex pictures with 16 million colors. people.scenes etc. 80% quality level is usually good for web.
@UNP: all babes are jpeg
problems: can't animate, no transparency.
tips: more than 60% surfers are still on 1024*768 or less resolution so resize your images less than that.
gif: supports animation and transparency, used for smiles ets.
@UNP: all smilies
problems: only supports 256 colors,complex images are bigger than jpeg
tips: use few and primary colors and save as 2,4,8,16... bit
PNG: supports transparency, looks better than gif/jpeg at same size.
@UNP: the header logo is PNG 8bit, same image in gif would be lot heavier and jpeg wouldn't be transparent
problems: transparency doesn't work correctly in Internet Explorers,A faint blue border is visible.
tips: use PNG 8bit.