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Images for the Web, August 2003
Without going into too much technical detail, you have probably seen these file extensions on images you have downloaded or used with e-mail. It may look something like this, "name.gif" or "name2.jpg", etc. Generally speaking, the GIF is best used for graphics such as cartoons or font images and JPEG (same as JPG) is best used for photographs. There are other formats, but the principles are the same for most.
Each image is a file and each file is made up of bytes. The number of bytes will determine how long the image will take to load. They can also determine how sharp the image is. Don't confuse the displayed dimensions (physical size) of an image with its file size. A common mistake I have seen by novice webmasters is using the width and height elements of an image tag to size the image for the page. On the next page is an example of this: Continued>>>