But even if you're positive that 100 percent of your site's visitors are using Internet Explorer and running Windows, it's still not a good idea to use bitmaps for Web graphics.
Bitmap files tend to be very large, even when the images are simple.
If you'd like to see what I mean, try downloading this graphic . You can probably imagine what images this size would do to your site's load time, and how many impatient visitors would end up being driven away. Instead of using bitmaps, you should convert your Web images to GIFs or JPEGs. This can be done with any image editor or image viewer. To see what a difference a change in file format can make, here's a GIF version of the image used in the preceeding paragraph's example.