I am trying to login from the admin side of my site. But it is not logging me in with the correct user-name and password provided.
I cleared browser history and tried in other browsers also.
It gives me an error :
Fatal error: Access to undeclared static property: Mage::$_isDeveloperMode in /home//public_html/one/em0113-full-package /app/Mage.php on line 881
Help me to resolve this issue.