App Tiles (Internet Explorer in the new Windows UI style UI)
No hi-res favicon : If your website does not have a favicon or its resolution is less than 64x64, a user that pins it will just see a small semi-opaque Internet Explorer logo.
IE9 hi-res favicon : If your website has already implemented favicons, a user that pins it will see your logo at its real size (64x64) leaving a lot of empty space.
Internet Explorer 10 Tile : If your website implements Internet Explorer 10 Internet Explorer in the new Windows UI tiles, a user that pins it will see your website's logo and will be able to easily identify your brand.
Favicon Checklist
Icon file (.ico format) with the logo in the following resolutions: 16x16, 32x32, 64x64
PNG file of 144x144pixels with the logo of the company
Hexadecimal color value of the tile
Permission to update the html content of the website
Permission to add image files to the web server
Name of the application
[Designer] Create an .ico image with your company logo with the following resolutions (resolutions here).
[Designer] Create a .png file of 144x144 with your company logo and a transparent background.
[Designer] Provide the assets to the developer.
[Developer] Put the assets the designer has given you (an .ico file and a .png file) in the web server. Those files have to be accessible from the Internet.
[Developer] Remember the URL to each of the files. It can be relative ("/favicon.ico") or absolute ("http://www.mydomain.com/favicon.ico").
[Developer] Edit the header section of the website.