find . -type f -exec chmod 644 {} ;
find . -type d -exec chmod 755 {} ;
chmod o+w var var/.htaccess app/etc
chmod 550 mage
chmod -R o+w media
If that is not working, try setting all directories to 777 by doing this:
find . -type f -exec chmod 644 {} ;
find . -type d -exec chmod 777 {} ;
chmod o+w var/.htaccess
chmod 550 mage

magento/app/etc
magento/media
magento/app
magento/skin
magento/var
magento/var/.htaccess
magento/js
magento/downloader
644權限
magento/index.php
magento/downloader/index.php

<?php
## 設置文件644，目錄755
function AllDirChmod( $dir = "./", $dirModes = 0755, $fileModes = 0644 ){
$d = new RecursiveDirectoryIterator( $dir );
foreach( new RecursiveIteratorIterator( $d, 1 ) as $path ){
if( $path->isDir() ) chmod( $path, $dirModes );
else if( is_file( $path ) ) chmod( $path, $fileModes );
}
}
?>