error 500 magento commerce when trying magento connect

looks like magento is famous for error 500 error . You need to be really good at searching and trying the right solutions to fix this .

so to install a them you need to goto system> magento connect > magento connect manager in the back end
boom! error 500!

1)went to the cpanel file manager
went to the magento install folder
went to the downloader folder
changed the permission of the folder to 755
this changed the permission inside the folder


http://xhtmlandcsshelp.blogspot.in/2010/09/magento-connect-manager-internal-server.html