A favicon is the small icon that appears in a web browser tab when someone visits your site. It will also be used when someone bookmarks your site.
Uploading a Favicon
Upload a favicon to your site by clicking Settings > Website > Favicon. Click Browse, select an image from your computer, and click Upload.
Creating a Favicon
For the highest compatibility with all web browsers, Favicon images should be in the .ico file format. Other file types – like .gif, .png, and .jpg – are not supported by Internet Explorer. Also, icon files should be 16×16 or 32×32 pixels in size, and 8-bit, 24-bit, or 32-bit color depth.
If you need help converting an image into an .ico, try these sites: