Unfortunately, for lack of a bit of knowledge, many webmasters, uninitiated and some of relatively experienced, are using images in such a way as to disadvantage themselves and their websites. The most common problem I see is images that are way to big (and I don't mean physical size), which only serves to slow their website's loading time. I've noticed there are a number of webmasters who either aren't aware of fact that a website is no place for a bitmap image (.bmp) or they don't know how to convert it to a more friendly file.

Firstly, we have to establish major file types (or file 'extensions') that are used on websites. These are, as I just mentioned, bitmap (.bmp), which is a MS Windows® format, jpeg (.jpg), gif (.gif) and to a lesser degree png (.png). These initials all have meanings, for instance 'png' stands for 'Portable Network Graphics' but it's really of no consequence to name them all.

As I said, except in a very few circumstances, bitmap images have no place on a website, simply because of size of file needed to carry them. They certainly have their uses but this isn't generally a recommended use because they can slow loading speed (the time it takes for a web page to appear on a user's screen) to a virtual crawl, unless they are a very small or 'simple' image in terms of color and content.