Questions

to make an image appear of the Internet quickly it has to be prepared - this is called optimisation.

1. there are 3 main image file formats in use: jpg, gif and png - the image file has to be in one of those formats, with an appropriated suffix (ie. myimage_1.jpg).
2. the image has to be in the right colour space: RGB (the CMYK colour used for printing will not show on the Internet).
3. the file has to be in right size to load quickly: the file size is reduced by: reducing the number of pixels (image size), compression (jpg) or reducing the number of colours (gif).

the image optimisation is a series of irreversible decisions, which result in a small, fast loading image. a number of free and commercially available programs (such as Photoshop) can be used for this purpose - make sure you keep the original file.

to optimise image as jpg in photoshop (depending on your version) is something like this:
- reduce the number of pixels:
-- Image > Image Sixe > set the number of pixels in width or height (resolution does not matter, traditionally, it is 72 pixels/inch for web)
- reduce size by compression:
-- File > Save As > format: JPG - choose Quality (Medium - High - Maximum)

other file formats in use (PDF, Flash, Shockwave, movie) need additional plug-ins to be viewed.