Using Permalinks « WordPress Codex

Using Permalinks « WordPress Codex: "You can edit the .htaccess file by FTP, shell, or (possibly) your host's control panel.

The following permalink rewrite code should be included in your .htaccess file (since WordPress 3.0):

# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress
If your .htaccess file contains errors that bring down your site ("Internal Server Error (500)"), you will need to use FTP or your host's control panel to delete the rogue .htaccess file."

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