Why my favicon not showing up, although it is defined correctly?

Late, however. I run into this problem more than I should. My fix is to add a 'version number' ?v1 or whatever, this will blow away cache.

<link rel="icon" href="favicon.ico?v1" type="image/x-icon" />
<link rel="shortcut icon" href="favicon.ico?v1" type="image/x-icon" /> 

It's probably just cached in your browser, it shows up as a blue cross on mine.

Else, check your image path. image/favicon.ico isn't matching images/favicon.ico, but that is probably just a typo.