oing illustration for the Web is a little different than creating images for print reproduction. The resolution at which it will be seen is lower and the color can change from computer to computer. Because there's always the potential for an illustration done originally for the Web to find use elsewhere, most artists work as though it were going to be printed. Then, a reduction in size and resolution is made to facilitate quick viewing through digital medias. Before the final reduction is made, a number of versions are tested for both both color and load time. Whenever possible, the average parameters that work best within a particular Web presentation are recorded and used for all its images. However, the usual benchmark that calls for a consistent look from page to page is not as severe on a Web site as it is in a book. This is due to the fact that online pictures appearing on different pages can't readily be seen side by side.
Should an image be converted to a jpeg or a gif?
The loose rule of thumb is that jpegs work best for photographs, especially those of people. Gifs on the otherhand are recommended for pieces that have less variations between tones. But when download time is thrown into the mix, the equation becomes a little fuzzy. All of a sudden, gifs begin looking attractive in situations where a long wait would be particularly obtrusive.