All you want to know about favicons in 2016 !
I wrote, in 2010, an article about favicon. However, with the mobile devices (iOs and Android), and Safari and the Windows Metro interface (introduced in Windows 8), a favicon.ico is not enough any more.
Nowadays, you need to generate 41 files to accommodate all the devices and software.
At the end of the day, the easy solution is to use realfavicongenerator.net !
Happy favicon generation ! !