You might get this error when you go to Magento Connect Manager (System -> Magento Connect -> Magento Connect Manager) of your Magento installation. This means that Magento Connect is unable to write files to your server.
Warning: Your Magento folder does not have sufficient write permissions.
The solution to this problem is to set all folders permission to 777.
Go to your installation root folder and run the following command (You should have access to SSH on your server to run this command):-
find . -type d -exec chmod 777 {} \;
Now you will not get the error on Magento Connect Manager and you will be able to install any extension from there.
Don’t forget to change the folder permission to 755 after you are done with installing your extension from Magento Connect Manager.
To do this, run the following commands:-
find . -type d -exec chmod 755 {} \;
chmod 777 var var/.htaccess app/etc
find var -type d -exec chmod 777 {} \;
chmod -R 777 media
Hope it helps. Thanks.