Image resolution also affects the size of an image. Most image editing programs have commands to change the resolution. For example, in Adobe Photoshop choose Image Size from the Image menu to set the resolution. Also make sure your graphic is not larger than 600 pixels wide. Images wider than that require scrolling on smaller monitors.
Most graphics applications have commands that display the size of the image in pixels.
For example, in Adobe PhotoShop choose Image Size from the Image menu to see the dimensions of an image. The figure below is an example of an image that is too large to fit within a standard browser window. The graphic is a GIF that is 720 pixels wide. Horizontal scrolling is taboo on the Web.