I developed a website, using php/mysql running at IIS Server as CGI Server API. Suddenly it gives me error 500 after two weeks. It has lot of scripts but index.php home is working. But other script that has header redirection What's wrong with my scripts. livehttp addon of firefox says.. GET /allplans.php?lang=ar&cat=1 HTTP/1.1 Host: www.myhost.com... [edited] User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:14.0) Gecko/20100101 Firefox/14.0.1 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8 Accept-Language: en-us,en;q=0.5 Accept-Encoding: gzip, deflate Connection: keep-alive Cache-Control: max-age=0 HTTP/1.1 500 Internal Server Error Content-Type: text/html Server: Microsoft-IIS/7.5 X-Powered-By: ASP.NET Date: Mon, 03 Sep 2012 08:09:13 GMT Content-Length: 1208 Connection: Keep-Alive