A favicon is the little icon that appears next to the webpage title in the browser tab. The favicon must be either 32x32px or 16x16px in size and must be either a .png, .gif, or .ico in order to work properly.

Once you have an image that fulfills these requirements, add the image to your website folder. Then just add this line to the <head> element of your html document (making sure to adjust the href and file type to match your file):

<link rel="icon" type="image/png" href="myicon.png">