Lets start with an example so you see where were going to with this article. Consider a listings type site; in this case, lets think of a real estate website which lists properties. Each property has a picture. You have a page where you list all properties in a given neighborhood, about 20 properties per page. For each property, you display a smaller version of its picture (this is called a thumbnail), and a brief description of the property, so site visitors can click on the property they like to learn more about it. The problem is: this page takes really long to display in the browser.
There is a high probability that this problem is related to the images. You need to analyze how your site generates the thumbnails. In many scripts, the thumbnails are just the original pictures, but displayed in smaller width and height. If this is the case, then each picture takes too long to load. You should change this approach and generate real thumbnails of each picture. You also need to change your script to work with the images thumbnails, and not just the original big images.
There are different ways to generate the thumbnails:
1) Using a graphics program. You load...