About half of all U.S. households have some kind of broadband Internet access, and many of those users don't have high-speed access at the office, school, public library.Even a low-end cable or DSL connection can pull down about 85 Kbps. The Internet has come a long way since CompuServe commissioned the creation of the Graphics Interchange Format in 1987 to speed up the delivery of images to its members
First, since the most common browser image formats are compressed formats, you don't have much choice.
There's no convenient way to put your EPS, TIFF, and native Photoshop files on a web page.
Sure, you can leave the compression options pegged to the top end of the scale when optimizing, but your images will still get compressed to some degree before they end up on your web site.
The second, more serious reason is conservation of bandwidth.(your visitors' and yours.) Optimizing web page code and images ensures that no one who visits your site waits too long for the page to load.
An website filled with poorly optimized sites would quickly eat up most of that high-speed access and leave those without it frustrated and looking at partially loaded pages. Also, large image files can quickly consume most or all of your web server disk quota and bandwidth limit, adding extra charges to your hosting account.
Once you know you need to optimize, it's largely a matter of choosing the right file format.
