Magento connect manager internal server error

This is the most common problem for all Magento User.This problem is only for the File Permission in the server.To solve this Problem first you need to login to your FTP(File Transfer Protocol), then go to your magento installation path their you will find downloader Change the file permission to 755 , Again goto the index.php file inside downloader folder and change the file permission to 755.Now refresh the page you will see the effect.