Description Of The Problem

A few days ago, I was facing a problem "Sharepoint anonymous site prompting for credentials on a mobile phone."

Resolution

To resolve this issue I have done the change in "compat.browser" file in the App_Browsers folder. Changes are done as below.
<!-- Android -->
     <gateway id="Android" parentID="Default">
         <identification>
             <userAgent match="Android" />
         </identification>
         <capabilities>
             <capability name="isMobileDevice"                        value="true" />
             <capability name="Platform"                              value="Android" />
         </capabilities>

And change it to:

<!-- Android -->
     <gateway id="Android" parentID="Default">
         <identification>
             <userAgent match="Android" />
         </identification>
         <capabilities>
             <capability name="isMobileDevice"                        value="false" />
             <capability name="Platform"                              value="Android" />
         </capabilities>

Before doing the above changes in the file I have taken the backup of the file i.e. compat-copy.browser. after a server restart, we received the following error.

Then I deleted the backup file "compat-copy.browser" after that site started working fine. 

So whenever you take a backup, make sure you change the extension of a backup file.