Working with images for the Web is very much an art! I don’t mean this in the sense that generally you should be quite artistic in order to make nice pictures. I mean that actually managing and dealing with image files is itself an art. There is a lot of work to be done for the aspiring website owner with respect to attaining a pleasing and meaningful visual environment. This is because the Web is the one retail environment that is most reliant on visual images to have an effect on customers because sight and sound are the only two senses that are targeted by the Internet, for now.
In order to have the freedom to manipulate images as required by your site, you really need to use a reasonably powerful image editor. Photoshop or Paint Shop Pro are examples of good image editing environments, but anything that allows you to save files in a variety of different formats and provides resizing capabilities should be sufficient for a simpler looking site. Of course, if you have...