The Exchange Forms Based Authentication login page settings are contained in the logon.asp page.  The steps below describe how to remove the option to choose a Premium or Basic experience from the OWA login page.  This is what the login option will look like after following the steps below:

 

 

 

To remove the Premium and Basic options,

1. On the server, navigate to \Program Files\Exchsrvr\exchweb\bin\auth\usa.
2. Backup the logon.asp file before making any changes to ensure you can revert back to the original file.
3. Open the logon.asp page using Notepad or Visual Studio .NET.
   
   Note: To ensure constancy, update the logon.asp page for each language OWA is accessed in by users in your organization.
   
   
4. Comment out the Basic and Premium text using single quote (‘) as shown below.
   'CONST L_ShowSimpleUI_Text = "Basic"
   'CONST L_ShowComplexUI_Text = "Premium"
    
5. Search for L_ShowUITitle_Text
6. Comment out: <!--" & L_ShowUITitle_Text & "-->
   
   
7. Search for L_ShowDetail_Text
8. Comment out: <!--Response.Write "(<A id=""lnkShowClient"" href="/" mce_href="/"#"" onclick=""onClickHelp();return false;"" >" & L_ShowDetail_Text & "</A>"-->
   
   
9. Search for L_HideDetail_Text
10. Delete only the closing bracket “)” near the end of the line: " & L_HideDetail_Text & "</A>)</TD></TR>"
    
    
11. Search for L_ShowComplexUI_Text
12. Comment out: ><!--<INPUT id=""rdoRich"" checked type=""radio"" name=""forcedownlevel"" value=""0"" onclick=""flags.value &= 14"">-->
    
    
13. Search for L_ShowSimpleUI_Text
14. Comment out: <!--<INPUT id=""rdoBasic"" type=""radio"" name=""forcedownlevel"" value=""1"" onclick=""flags.value |= 1"">-->
    
    
15. Save the changes and verify the logon page.

For more information on customizing the login page, refer to the following Microsoft article: Customizing the Outlook Web Access Logon Page.