title: hide a field using controller extension in salesforce
body: <p>I am new to salesforce development.
  I have a requirement where not much customozation is needed but need to hide or show a couple of fields based on a value of other field. 
  Can I do this using standard controller and adding an extension controller? if yes How?
  e.g I need to show the standard account page with list of accounts. when I click on a account , on the standard detail page there is a field " Rate". if the Rate is below 10% then I have to show "Revenue " field and if its >10% then I have to hide the previous field and show "Approx. Revenue" field.
  Is this possible?
  THnaks</p>