I got a serious problem while changing pemalink style in admin settings of wordpress site. It was showing 404 for every posts/pages accept the home page. I really dont know what would be the solution. My dear fellow colouge Russel Vai helped me to solve this problem. The problem was with the .htaccess file in base path. So if this problem arrise first check the base path in .htaccess file. Though we figured it out later. We did some other process earlier and got it right. We first took a backup of the .htaccess file and deleted it from the server with ftp. Then we set the permalink in default mode and changed to it to my desired custom mood later. And it returns the posts/page which shows 404 to actual content. What it did actually it regenarate the .htaccess file automatically while changing the permalinks type in admin panel.