Here is the code required to add icons on apple supported devices.

With Apple’s Reflective Shine:
< link rel=”apple-touch-icon” href=”somepath/image.png” / >

Without Apple’s Reflective Shine:
< link rel=”apple-touch-icon-precomposed” href=”somepath/image.png” / >

The recommended basic size for this icon is 57×57 pixels, with 90 degree corners; for best display on the higher-resolution iPhone 4 screen, an icon size of 114×114 pixels is recommended.[29][31][32]
For the iPad and iPad2, the basic size is 72×72 pixels with 90 degree corners. If the rumored next generation follows the same pattern as the iPhone and iPodTouch, the high-resolution size would be 144×144 pixels.[33]

Also see my other article

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I Grabbed this off the wikipedia page:

Google Chrome Internet Explorer Firefox Opera Safari 
<link rel="shortcut icon"
 href="http://example.com/myicon.ico" />
 Yes[4] Yes[4][17] Yes[4] Yes[4] Yes 
<link rel="icon"
 type="image/vnd.microsoft.icon"
 href="http://example.com/image.ico" />
 Yes No[23] Yes Yes Yes 
<link rel="icon" type="image/png"
 href="http://example.com/image.png" />
 Yes No[23] Yes Yes Yes 
<link rel="icon" type="image/gif"
 href="http://example.com/image.gif" />
 Yes No[23] Yes Yes Yes
favicon.ico located in the web site’s root Yes Yes Optional[24] Optional[25] Yes
precedence: prefer root or (X)HTML linked version ? root[21] ? ? ?
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