htaccess不支持centos 6 vps托管

Question

我的vps上有两个网站托管一个Codeigniter，另一个是普通的php。他们都有htaccess，问题是Codeigniter的htaccess工作，其他网站的htaccess不是。 这是htaccess

RewriteEngine On
RewriteRule ^index?$ index.php
RewriteRule ^today.html?$ today.php
RewriteRule ^tomorrow.html?$ tomorrow.php
RewriteRule ^contact.html?$ contact.php
RewriteRule ^tag/([0-9a-zA-Z-_]+).html tag.php?tag=$1