Magento Add the Default Permission for Folders

Folder permissions

/media - accessing the product images
/var - generating the cache, report files

Downloader, var and media folders are need be writable
[magento_root_folder]/var - 777 [magento_root_folder]/media - 777 [magento_root_folder]/downloader - 777

Once completed instllation and development process.
Reset back downloader folder to 755 so that this folders are non-writeable in production.

For files keep the permission as 644.