You should use both of these lines: Just so you can accomodate this for all browsers.
<link rel="icon" href="/favicon.ico" type="image/x-icon">
<link rel="shortcut icon" href="/favicon.ico" type="image/x-icon">
For creating the icon, you can even use MS Paint and save the as favicon.ico, however better the image quality tool, better the icon will look in terms of its clarity. But at least something for you to start playing with.