Wordpress generates an .htaccess file when the permalinks are changed that contains the rewrite directives. It sometimes happens that the file cannot be created or written which would then mean that the user would need to create and edit the htaccess file manually. The Wordpress code that is used is not optimized. It does not prevent for instance unnecessary file and directory checks. JP Morgan over at the Webmaster World forum created a better rewrite directive that “fixes several performance-affecting problems”.