What is a Favicon?
Traditionally this was a small square 16 x 16 or 32 x 32 pixel graphic representation of a website or webpage that appears in the browser address bar, browsing tabs, next to the site name or URL in a bookmark list, or in a shortcut link on a desktop. It is a portmanteau word from the words “favorite” and “icon”.
Because it is a very small image, frequently a letter, logo or part of a logo are used.
Why is it important?
In my opinion they are important because if you don’t have one, then a user with many tabs open, depending on the browser, will be unable to identify your site. A blank marker will appear or a marker provided by the hosting company. A favicon improves user experience, and probably decreases the probability of someone abandoning your site.
How can I get one?
Contact your web developer or if you want to load one yourself, there are umpteen favicon generators available online. You can either create one from scratch or use an existing image. Faviconer.com will create a 24 bit favicon.ico with a transparent background. Also check favicomatic, Dynamic drive, and X-Icon Editor. Follow the instructions on the website and download the image to your computer.
Interestingly enough, I have noticed that many websites, even international websites don’t have them. I consider that a missed opportunity. It is so difficult to be found on the internet; surely this additional step to retain users is worthwhile?
What type of file? .ico, .png or .gif?
The original favicons were a 16×16 bit favicon.ico file. Today modern browsers accept .png or even .gif images. The question is what kind of web browser compatibility you are interested in? Who are your target audience? For older browsers,16×16 favicon.ico is the safest bet. Some developers will load multiple files with different resolutions up to 228 x 228 in order to be compatible with modern browsers and Retina display. See the Favicon Cheat Sheet.