Unable to remove ??? this line from default.aspx using powershell

Question

Trying to open the default.aspx page using powershell script
$file =  $spSourceWeb.GetFile("default.aspx")
 $datastring = [System.Text.Encoding]::ASCII.GetString($file.OpenBinary()) 
in the content I am getting three ??? char because of this site is breaking . how to avoid this or remove .please provide your suggestion on this .
sarav

Answer 1

I am tring to download the default.aspx page from subsite  then remove some bad reference from default.aspx then then again planning to update.
My code here
if((Get-PSSnapin | Where {$_.Name -eq "Microsoft.SharePoint.PowerShell"}) -eq $null)
  Add-PSSnapin Microsoft.SharePoint.PowerShell;
try
    #set the admin url
    $sourceWebURL = "My url"   
    $spSourceWeb = Get-SPWeb $sourceWebURL
    $file =  $spSourceWeb.GetFile("default.aspx")   
    if ($file.ForceCheckout)
        $file.CheckOut()
    #download files
    $datastring = [System.Text.Encoding]::ASCII.GetString($file.OpenBinary())     
    $strFinder = '<%@ Register TagPrefix="WpNs1" Namespace="BD.Evolve.DHFQueryWebPart" Assembly="BD.Evolve.DHFQueryWebPart, Version=1.0.0.0, Culture=neutral,    PublicKeyToken=709ed70a96eaa5cb"%>'
    $strReplace =''   
   # Need to replace ???
    $strFinder1="???"
    #Write-Host $strFinder1    
    #$datastring=$datastring -Replace($strFinder1,$strReplace)
    $datastring=$datastring -Replace($strFinder,$strReplace) 
    $file.SaveBinary([System.Text.Encoding]::ASCII.GetBytes($datastring))   
    if($file.CheckedOutBy.LoginName -eq 'my adminid')
     $file.CheckIn('myadminid');
    Write-Host $datastring
catch
        Write-Host "error "+$error[0]
sarav