You want to hide the Created by , Modified by columns which appears on all the SharePoint list by default. There are many ways to achieve this. We always create a view for the list with the necessary columns excluding the user information. Below lines of PowerShell Commands will solve our purpose as well.
$SPweb=Get-SPWeb "http://mysite/SampleSite"$SPlist=$SPweb.Lists["CustomList"]$SPlist.ShowUser=$false$SPlist.Update()
* CustomList is the List name.
*ShowUser is the property which is set to true by default. We need to change it to false!!! Fair enough!!