A picture's worth a thousand words. An old saying, but true enough on the 'Net where you can transfer chapters of text in the time it takes to download just one big image. Ever notice how pictures are always the last thing to show up when you're websurfing? That's because the biggest hunk of download time comes from the image files.
Over the next four days, we'll be looking at all the different ways to get pages down to their leanest and meanest. Today we start with the most egregious and most obvious culprit: images.
By the way, a lot has changed since the first edition of this tutorial there's more to optimizing image performance today than just knowing your GIFs from your JPEGs. (Though we'll review that, since this may be your first time around.) There are now new file formats (like PNG) worth considering, and improved weighted-optimization techniques to throw into the mix.
And, hey, quite a bit hasn't changed. For one, Web users haven't gotten any more patient. It doesn't matter how ice-cool your images may look if they can't be downloaded quickly over a 56K modem, very few people will stick around to see them.
Fortunately, there's still a host of tricks and optimizations that Web designers can implement to speed image downloads. Let's start with the easiest thing in the world.