on Screen

When developing images for the web or images that will primarily be viewed on a screen; the size of the images depends on the screen resolution of the viewers monitor. Not pixels per inch.

It is said that 72 ppi is ideal for a image that is to be viewed on screen. This fact is out-dated. Screen resolution is not measured inches, dots, or any other measurement of the physical world. Screen resolution is measured in pixels.

So, when developing an image for screen, specify the images width and height in pixels. Keep in mind that people are viewing from many different monitor sizes; set to many different screen resolutions.

Most users have 1024x768 or higher, but a large minority have
800x600. These numbers do not include those who browse using web appliances.